After setting up his personal security systems and piling pillows against the door so no one in the hallway could eavesdrop, he sat on the bed, anxious and alone, in a Hong Kong hotel room. He was 29 years old that night, May 24, 2013, but he looked much younger, thin and pale, like a college kid, in his blue jeans and white T-shirt. Someone who talked to him later described him as “terrified,” and it’s easy to believe. He was walking away from everything he had ever known, his career, his girlfriend, his entire life, and now it appeared that his plan might fall through.

He had come to Hong Kong four days earlier, his luggage filled with laptop computers and thumb drives containing tens of thousands of secret documents he had stolen from the U.S. government—documents that, he felt sure, would demonstrate how far overboard America had gone to protect itself from enemies real and imagined. But time was running out. Soon his superiors would come looking for him, if they weren’t already. Before they did, he needed to give his documents to a journalist who would share them with the world, but none of the three he had contacted had yet traveled halfway around the planet to meet with him. Just that night the one who wrote for The Washington Post had passed.

If it really had all been for nothing, if he really had spent months plundering government computers for secrets no one would ever see, the best he could hope for was asylum in a foreign country—maybe Iceland, maybe Ecuador. If he failed, they would lead him away, in handcuffs, to prison. Or, he thought, maybe they’d just kill him.

It had all begun some six months earlier, the way the best spy thrillers do, with a whisper in an exotic locale. This time, as befits the defining espionage story of our age, the whisper was first typed into a computer and sent to an expatriate American columnist and former lawyer living in a greenery-shrouded villa in Rio de Janeiro, then to a provocative documentary-film maker at her apartment in Berlin, and last to a Pulitzer Prize-winning journalist in his office in downtown Manhattan. The columnist, a 47-year-old named Glenn Greenwald, ignored that strange first overture. Greenwald had transformed himself into a crusader in the fight against aggressive government surveillance. His columns and blog posts for Salon, and for a British newspaper, The Guardian, had won him a devoted following among a broad coalition of civil-rights and privacy activists. That first e-mail, one of many that had popped onto his laptop on the morning of December 1, 2012, was cryptic. The anonymous sender, saying he had information Greenwald might be interested in, asked for his public encryption key (a so-called P.G.P. key), so they could have a secure online discussion. Greenwald didn’t have a P.G.P. key and wasn’t going to the trouble of getting one for so vague a promise.

But the sender, whoever it was, wouldn’t give up. He sent Greenwald encryption tutorials, one on video. Again Greenwald balked. Now he had to watch a video? And for what? The sender still wouldn’t give any sense of what he was offering. After a month of fruitless back-and-forth, Greenwald put it aside, and the sender vanished back into the ether.

Next, in late January 2013, the sender e-mailed documentary-film maker Laura Poitras. After appearing on a U.S. “watch list,” Poitras, 50, had been detained and searched dozens of times at international borders and had fought back against invasive government surveillance. The e-mailer had read about her in one of Greenwald’s columns and had seen a short documentary she had made on domestic spying by the National Security Agency, the giant U.S. government entity whose computers hoover up and analyze all manner of electronic communications from countries around the world.

Poitras had a P.G.P. key readily at hand, but the sender’s next e-mail instructed her on how to get on an even more secure system. Once there, he assured her, “I am a senior member of the intelligence community. . . . This won’t be a waste of your time.”

Poitras, possibly more wary than the sender at this point, responded, “I don’t know if you are legit, crazy, or trying to entrap me.” He replied, “I’m not going to ask you anything. I’m just going to tell you things.” Poitras asked if he had seen the government’s file on her. He said no. He claimed he was contacting her because she’d been persecuted by the system he wanted to expose: “I bet you don’t like this system,” he wrote. “Only you can tell this story.” The sender seemed legitimate, but Poitras was still nervous. She needed advice from colleagues with legal and national-security expertise.

In early February, Poitras reached out to Barton Gellman, the Pulitzer Prize-winning journalist, who had covered national security for The Washington Post. “Laura asked if I could meet to talk about something confidential,” Gellman recalls. “And we both knew what she meant by confidential. She wanted to make it as private as we could make it.” Using encrypted messages as a precaution, they arranged to meet at a café in New York City’s West Village and, once there, walked to another café, to avoid anyone who may have learned of their meeting. After that, from time to time, Poitras would tell Gellman something her source was saying, and he would give her his impressions. The more it went on, the more they were both convinced that this was real.

After the source described to Poitras secret government surveillance programs, she arranged to meet with her colleague Glenn Greenwald at a New York City-area hotel, where he was attending a conference. Poitras insisted he not bring a cell phone; the N.S.A., she knew, had the ability to turn any mobile phone, even one that had been turned off, into a microphone. She had printed the sender’s e-mails, and Greenwald read them and shared her excitement.

In early May, Gellman began receiving cryptic messages of his own. The sender used a code name, “Verax”—Latin for “truth teller”—and again suggested he had something to offer. A few weeks later Verax sent Gellman a PowerPoint presentation outlining an N.S.A. program called “Prism,” which secretly gathered data from technology companies such as Google, Microsoft, and Facebook. Gellman recognized the explosiveness of the story and met with his editors at The Washington Post to get them on board, but then Verax asked that the paper print the article on Prism within 72 hours. Gellman said that the paper couldn’t promise to publish on a particular date, and would need far more time to authenticate the sender’s claim.

The source then turned back to Poitras, who again brought in Greenwald. In late May the sender finally asked to meet with them—in Hong Kong. At that point things got even more complicated. Because Greenwald worked for The Guardian, the trip—indeed, the entire endeavor—now became a Guardian project. But he had worked at the paper for less than a year, and because he lived in Brazil, and the paper’s main office was in London, with a satellite office in New York, few of its editors knew him well, much less trusted him with such an important assignment. On Friday, May 31, after he and Poitras arrived at The Guardian’s loft-style U.S. offices, in the SoHo neighborhood of Manhattan, the paper’s U.S. editor, Janine Gibson, decided the pair needed a chaperone—a trusted Guardian veteran reporter. She summoned her 61-year-old Washington correspondent, Ewen MacAskill.

From the outset, the chemistry was strained. MacAskill, an affable Scot who spoke with a thick burr, didn’t know Greenwald and sometimes found his writing “strident.” Poitras was not asked to the meeting, so she sat alone at the far end of the newsroom, “hostile” in MacAskill’s view. She was unhappy at the prospect of introducing another journalist into the mix. When everyone else sat in Gibson’s office to review the Prism documents, MacAskill was unmoved. “I didn’t know anything about the N.S.A.,” he says. “I couldn’t grasp the significance of what we were looking at.”

Afterward, Poitras was terribly upset, warning Greenwald that they were jeopardizing the entire project by taking along a Guardian reporter to Hong Kong. The source was expecting two people; if he saw a third, he might bolt. But the editors wouldn’t budge.

The next morning, when Greenwald and Poitras rode in a cab to Kennedy airport, Poitras was still nervous about including MacAskill. MacAskill, meanwhile, was worried about the Guardian communications’ being monitored, and had worked out a coded exchange in which he could indicate the source’s veracity to his bosses. An editor was to ask: “How’s the Guinness?” If the source was genuine, MacAskill was to respond, “The Guinness is good.”

The Guinness, as the world now knows, turned out to be very good indeed. What the three journalists discovered upon their arrival in Hong Kong, it seems safe to say, was the single greatest journalistic coup since the Pentagon Papers. The mysterious e-mailer was a young computer technician named Edward Joseph Snowden, who is now regarded as the most important whistle-blower of modern times. Snowden’s is that rare story the importance of which is almost impossible to overstate. His revelations have triggered investigations by a presidential commission and several congressional committees, while putting immense pressure on American diplomatic relations with scores of countries—from Germany, where, Snowden revealed, the N.S.A. had monitored Chancellor Angela Merkel’s cell phone, to Brazil, where it had done the same to President Dilma Rousseff’s. The Snowden affair triggered something like panic in the intelligence community and put the Obama White House on the defensive for months. The repercussions, it seems clear, are likely to persist for years, perhaps decades. Insofar as they lead to changes in the vast electronic-surveillance bureaucracy Washington has built since the terrorist attacks of 2001, America will never again defend itself against its enemies in quite the same way. “He’s not just revealing this report said that or this—that is like water dripping out,” says former C.I.A. director and N.S.A. chief Michael Hayden. “In Snowden’s case, it’s not just the buckets he’s dumping—he’s revealing the plumbing.”

The N.S.A. laid bare in Snowden’s documents is an agency that has the capacity to collect data about virtually every phone call made in America, not to mention hundreds of millions of calls overseas. In order to collect even broader swaths of data, the agency works with its British counterpart, the Government Communications Headquarters (GCHQ), to intercept communications traveling over fiber-optic cables running between the data centers of Internet companies. The N.S.A. has infiltrated video games, cell-phone apps, and every corner of the digital universe, looking for suspicious activity. Whenever it came up against a locked door online, protected by encryption, the N.S.A. attempted to break in, both by attacking specific encrypted material and by creating weaknesses, or “back doors,” in encryption platforms. Inevitably, much of the information amassed—in fact, most—was about ordinary American citizens suspected of no wrongdoing.

The revelations have challenged basic assumptions about what is private, ripping open debates, long festering, about safeguarding our nation versus safeguarding the Constitution. They have raised questions about whether we should be able, either collectively or individually, to keep a secret. Because of Snowden, we suddenly live in a very different world. People trust the Internet and their devices much less than they did, because it is understood that those devices can be used not only against individuals but also to control society and politics. Governments, meanwhile, are taking evasive and defensive actions. Hackers and the tech community are looking hard at new ways to ensure secure communications—at least for themselves, if not for everyone. “We were sleepwalking into abandoning our privacy, and Snowden has woken us up,” says David Cole, a professor of law at Georgetown University Law Center, who specializes in national security and constitutional law.

Nevertheless, Snowden himself seems to be viewed with profound ambivalence by many Americans. Few, it appears, believe the country is worse off knowing what he has shown us. But many are not entirely comfortable with the way he did it. Is Snowden a hero for our times—“a modern-day Nathan Hale,” in the words of another famous whistle-blower, Daniel Ellsberg? Or is he, in fact, a traitor?

Defending his motives in responses to Vanity Fair seeking to correct the record and amplify his views, Snowden says, “Every person remembers some moment in their life where they witnessed some injustice, big or small, and looked away, because the consequences of intervening seemed too intimidating. But there’s a limit to the amount of incivility and inequality and inhumanity that each individual can tolerate. I crossed that line. And I’m no longer alone.”

Whatever you think of Snowden, there is no denying he has emerged as one of the most compelling figures of the young century. The Jason Bourne-like aspects of his story—the cinematic international manhunt for the hero who says he only wants the truth to be known—alone are enthralling. A company in Oregon has issued an Edward Snowden action figure. This story, based on dozens of independent interviews, given both to Vanity Fair and to others, is an attempt to take a closer look at Snowden himself and to explain how a seemingly aimless, geeky kid from the Maryland suburbs found himself in possession of America’s most carefully guarded secrets in a Hong Kong hotel room with pillows piled against the door.

Edward, the second of Lon and Elizabeth “Wendy” Snowden’s two children, was born on June 21, 1983, in Elizabeth City, North Carolina. A port town on the Pasquotank River, two hours north of Cape Hatteras, the city is home to the largest United States Coast Guard air base in the nation, now run by the Department of Homeland Security. Generations of Snowden men were in the Coast Guard, including Edward’s father and grandfather. The Snowden clan—many of them military men and law-enforcement officers—is one of the area’s oldest; out on a country road next to the Rehoboth Baptist Church, in the town of Maple, Snowden Cemetery has family headstones dating back to 1886. Described as hardworking, conservative, and proud, the family reflects a traditional vision of America—“BSA” is etched into one young relative’s gravestone, for Boy Scouts of America. Nevertheless, it wasn’t particularly prominent. Before Edward made international headlines, only his grandfather Lonnie Glenn Snowden had left much of a public record. In November 1964, in the dead of night he lost control of his new Ford on a rural road, killing his passenger. He died less than four years later, at the age of 36, when, in the early-morning hours, he again lost control of his car, which ran off a country road into a canal. His son, Lon, who was 7 when his father died, was 18 when he and Wendy Barrett got married, in 1979, just out of high school. Edward was born four years later.

Snowden’s mother hasn’t given interviews about her son, but his father, a retired Coast Guard officer who now lives in Pennsylvania, has described him as a “gentle” child of exceptional intelligence. In 1992, when Edward was nine, the family moved to Crofton, Maryland, just west of Annapolis, and within 15 miles, as it happens, of N.S.A. headquarters, at Fort Meade. With stately brick and clapboard homes on winding streets shaded by towering oaks, Crofton is a well-to-do company town, home to thousands who work in the military and the intelligence community. Among Edward’s new classmates were children whose parents could not say where they worked.

Edward entered Arundel High School in the fall of 1997. In the fall of 1998, he became ill with mononucleosis and missed several months of school. He never returned, dropping out before completing his sophomore year. He then embarked on what, from the outside, appeared to be years of teenage slackerdom. In retrospect, however, they must be considered as a period of extraordinary self-education involving computer technology and the possibilities of the Internet. He also took a number of advanced community-college courses, earning an advanced certification as a systems engineer.

In fact, for five years, from the age of 15, he appears to have spent much of his time on this or that computer. In 2002, after a bitter divorce from her husband, his mother bought a condominium in nearby Ellicott City and let Edward live there. Joyce Kinsey, who lived across a walkway, paints a vivid portrait of watching Snowden at a laptop in his dining room hour after hour after hour, his concentration intense, into the late evening, then past midnight, and on toward daybreak. “I was interested in figuring out how complex systems fit together, so I put them together and tore them apart,” Snowden recalls of this period in his life. “All day, all night. I learned things that have helped me again and again in life.”

In person Snowden was reserved, a bit on the quiet side. But in the virtual world he could be clever, arch, and witty. Much of his online evolution can be traced in postings he made in a chat room of a technology Web site called Ars Technica. (Ars Technica is owned by Condé Nast, which publishes Vanity Fair.) In what is believed to be his very first posting, in December 2001, he wrote, “It’s my first time. Be gentle,” and followed up with questions about how to set up a Web server. His username was TheTrueHOOHA. In his subsequent early postings one can see a bit of pomposity, the pretentiousness not uncommon in an intellectually ambitious teenager. He referred to Newton and Goethe and mused on the nature of freedom. “It is the confidence of purpose,” he noted, “that allows you to be truly free.”

His life wasn’t all online, of course. Around 2002 he joined a group of friends who were devotees of anime—a style of Japanese animation with a near-cult-like following among computer geeks—and became their Webmaster. They hung out in the Fort Meade area and, as the Web site attests, engaged in a lot of age-appropriate silliness. There are photos of Snowden pulling down his pants to moon the camera in black underwear; with clothespins on his shirt over his nipples; in a tuxedo, dancing; in a leather jacket, in a car, with the caption “So Sexxxxy it HURTS! Ed Snowden, Gold Plated Xtacy.” On one of the photographs he wrote, “I like Japanese, I like food, I like martial arts, I like ponies, I like guns, I like food, I like girls, I like my girlish figure that attracts girls…. I really am a nice guy, though. You see, I act arrogant and cruel because I was not hugged enough as a child, and because the public education system turned it’s wretched, spiked back on me.” (Many Snowden observers have said it is unfair to judge him by the online posts allegedly made by him when he was young, even though they have been pored over by investigators trying to understand him.)

It was all good fun, but it wasn’t much of a life for a bright 20-year-old. As Snowden put it on Ars Technica, he was a man “without a degree or [security] clearance who lives in Maryland. Read that as ‘unemployed.’ ”

It was 9/11 that helped him point his way forward. Snowden has indicated that the attacks had a deep effect on him, and he favored the invasion of Iraq. In May 2004 he did what many under-employed 20-year-olds do: he joined the army. He said later, “I felt I had an obligation as a human being to help free people from oppression.”

Snowden reported to Fort Benning, Georgia, for basic training. He had enlisted in the army’s “18X” program, as a Special Forces recruit. He soon grew disillusioned, he has said, because he thought many of the other recruits seemed less interested in helping oppressed people than in killing them. Soon after arriving in Georgia, he broke both his legs in a training accident and, in September, he returned to Maryland, where he found a job at the University of Maryland’s Center for Advanced Study of Language—as a security guard.

Then the seemingly impossible happened. In mid-2006, barely 18 months later, Snowden got the job of an adventure-hungry young man’s dreams: he was hired by the Central Intelligence Agency as a computer engineer.

It’s so outlandish it seems like the plot of one of the computer games Snowden loved: aimless slacker hired by world’s top spy agency and given access to highly classified documents. Snowden himself could scarcely believe it. “I don’t have a degree of ANY type,” he wrote on Ars Technica that May. “In fact, I don’t even have a high school diploma. That said, I have $0 in debt from student loans, I make $70K, I just had to turn down offers for $83K and $180K (they’re going in a different direction than where I’m heading), and my co-workers have BSs, MSs, and ten to fifteen years of experience. Employers fight over me. And I’m 22.”

These many years later there has been considerable speculation about how Snowden got the C.I.A. job. In fact, it isn’t hard to understand. He was part of the small army of tech-savvy people the C.I.A. hired in the early 2000s to do battle with our enemies in the virtual universe. This wave of new hires was the C.I.A.’s belated attempt to catch up with a world—and a series of external threats—that had changed radically since the end of the Cold War, when grappling with Communist countries had been its core mission. When the Soviet Union imploded, in 1991, not only the C.I.A. but all the other U.S. intelligence agencies as well went through a crisis of purpose. It seems ridiculous now, but before 9/11 there was a moment when there seemed to be no overarching external threat to American security; some historians even threw around terms such as “Pax Americana” and “the end of history.” The country’s intelligence budgets were slashed, and staffing was cut dramatically—some 23,000 jobs by one estimate.

The 9/11 attacks woke America from its slumber. The C.I.A. and other law-enforcement agencies were blamed not only for failing to avert the plot but also for not even sharing information among themselves that would have revealed the hijackers’ presence in the United States. That collective failure produced a new mantra heard throughout the intelligence world: “Connect the dots.” That meant new and stronger computers, thousands of them, many with access to millions of pages of government information, so intelligence could be better shared and analyzed.

In the intelligence community, power shifted downward, from senior agents, who often had trouble even logging on to their computers, to junior staffers with expertise in the new tools of spycraft. This younger crowd didn’t have much use for the institutional hierarchies favored by the Old Guard. Attempts to bridge the generation gap were sometimes awkward. The head of the N.S.A., Keith Alexander, a four-star general, appeared in July 2012 at a DefCon hackers’ conference wearing a black-and-white T-shirt and jeans instead of his decoration-resplendent uniform, to make a plea to the conference attendees: “You’re going to have to come in and help us.”

Snowden was hired not as a spy but to maintain the computer system’s network security. The job required him to have a top-secret security clearance, a decision that has raised eyebrows in some quarters, given what Snowden eventually did with it. Talk to people inside the agency, however, and this is a non-issue. As the defense-and-intelligence world dramatically expanded after 9/11, security clearances were handed out like Kleenex. Today nearly five million Americans have some kind of security clearance, and about 1.4 million of those have a “top secret” clearance, many granted after background checks performed by private contractors focused more on speed, volume, and profit than on thoroughness. One former C.I.A. official points out, with justification, that there was nothing in Snowden’s background that would have prevented him from getting a top-secret clearance. “He was so young,” says this person. “He didn’t have a history.”

In early 2007, after barely nine months on the job, Snowden was transferred to Geneva, for which he was given diplomatic cover at the U.S. Mission to the United Nations. The mission there is a glittering block of steel, concrete, and glass, bordered by wooded parkland, near Lake Geneva. It houses the offices of the U.S. representatives to several international groups, including the World Trade Organization.

Snowden had a four-bedroom government-issue apartment near the lake. On Ars Technica, where he remained an active poster, he described his life in Switzerland as though he were a character out of a James Bond novel. He traveled extensively—to Bosnia, Romania, Spain—racing motorcycles in Italy and making friends with an Estonian rock star. He had a new BMW, from which he had the electronic speed limiter removed, and he began investing in the stock market—at one point bragging that he had lost $20,000 in a single month.

Snowden’s reaction to his new life underscores how very young, even parochial, he still was. On Ars Technica, he joked, “I’m living in Switzerland. I’m the straightest looking man in the country.” In London he found Muslims “terrifying…. I didn’t want to get out of the car.” Overall, though, Snowden seemed to have been happy enough—things were “pretty cool,” he wrote at one point. The “girls” in Switzerland were “gorgeous.”

In 2008 he opened a new thread on Ars Technica and said he’d had a vision in which his avatar’s true name had emerged from his subconscious and “flashed visibly in that moment of unrestrained spite; in the indulgent teabag.” His new gamer name: Wolfking Awesomefox.

Today, Snowden says that he was “drawn to the C.I.A. by a sense of duty, a desire to contribute. I wanted to do the hard work, not the easy stuff.” But in Geneva his feelings toward his new job grew more complex. In fact, he has said, it began to sour him on intelligence work. He would later tell The Guardian he had been deeply disturbed by an incident in which C.I.A. agents got a Swiss banker drunk and encouraged him to drive. When the man was arrested, Snowden claimed, the agents offered to help in exchange for the banker becoming an informant. Snowden has hinted that this was only one of many such incidents that troubled him. “Much of what I saw in Geneva,” he said, “really disillusioned me about how my government functions and what its impact is in the world.”

Mavanee Anderson, a onetime legal intern at the Geneva mission, wrote last summer in the Chattanooga Times Free Press of her friendship with Snowden during this period. She recalled that he seemed to be wrestling with “a crisis of conscience of sorts.” In contrast to his sometimes flamboyant online persona, she said, Snowden was far more pensive, far gentler—an “I.T. genius” who took his martial arts very seriously. She described him as “kind and sincere,” “introspective,” and “a bit prone to brood.”

Snowden has said he first contemplated leaking confidential documents around 2008. What information he had to disclose at that point isn’t clear, although a former C.I.A. official says his access to computers meant “he was in the system. He was reading the traffic” at the Geneva C.I.A. station. But Snowden held back, in part because he believed Barack Obama, elected that November, might introduce reforms.

A rare glimpse of Snowden’s internal conflicts during this period emerged in an Ars Technica message that has since been widely quoted. It came in the form of a comment on a January 10, 2009, New York Times story, citing unnamed officials who discussed the Bush White House’s covert plans to sabotage Iran’s main nuclear facility. Snowden expressed outrage at both the Times and its unnamed sources. “They’re like WikiLeaks…. They’re reporting classified shit,” Snowden wrote. “Who the fuck are the anonymous sources telling them this? Those people should be shot in the balls…. HELLO? HOW COVERT IS IT NOW? … THAT SHIT IS CLASSIFIED FOR A REASON.”

The next month Snowden resigned from the C.I.A. The circumstances remain in dispute, but it appears to have been ugly. Two senior American officials, speaking on background, told The New York Times last October that he had received a derogatory comment in his personnel file from a supervisor who said he had suspicions that Snowden was trying to break into unauthorized computer files and that, as a result, he had been sent home. (The day after the story ran, the C.I.A. issued a statement denying this account.) Snowden gave his version to the Times in an online interview: while angling for a promotion, he had gotten into a “petty e-mail spat” with a senior manager over flaws Snowden had discovered in the C.I.A.’s human-resources software. His immediate boss told him to back down, but then allowed him to test the system. Snowden said he altered some of the code in an attempt to highlight the software flaws; his boss signed off on it, but the senior manager became “furious” and took his revenge in the unflattering personnel comment. The incident convinced him, Snowden says, that trying to work through the system would lead only to reprisals.

A retired C.I.A. official who has made informal inquiries about Snowden in Geneva says he sensed broader differences at work. “Part of the problem was that he was too smart to be doing the job he was doing,” this man suggests. “I think he would have liked to have been a player.”

Whatever happened, by the time Snowden returned to the U.S. he seemed to be angry. Gone was the shy kid who had asked others on Ars Technica to “be gentle.” Now, when his opinions were challenged, he would respond by calling the challengers “fucking retards.” He termed Ben Bernanke, the Federal Reserve chairman, a “cockbag.” He railed against Obama’s support for an assault-weapons ban. Social Security outraged him. “Cut this social security bullshit,” he wrote at one point. On the subject of a safety net for the elderly, he wrote, “They wouldn’t be fucking helpless if you weren’t sending them fucking checks to sit on their ass and lay in hospitals all day.” Snowden says today that he is amused by reports of his “right-wing politics, based on what seem to be Internet rumors and third-hand information, and I have read it with some amusement…. I support a guaranteed basic income, I think we should take care of sick people, I believe women can make their own choices, and that the government is at its best when it’s building bridges instead of bombs. Does that sound right-wing? But I also think it’s common sense that people have individual rights, a right to be left alone, and a right to protect our families from violence…. Personally, I’d describe my political thought as moderate.”

His earlier online comments suggest frustration at losing his dream career. In any event, he wasn’t unemployed for long. As far back as his early teens, he had been intrigued by the idea of living in Japan. In early 2009 he got the chance, accepting a job with Dell in Tokyo. In addition to making computers, Dell managed computer systems for hundreds of corporations and more than a few government agencies. In Japan, Snowden worked at the Yokota Air Base, outside Tokyo, where he instructed top officials and military officers on how to defend their networks from Chinese hackers. There he also designed a highly sophisticated data backup system called EPICSHELTER. It used an advanced technology to place a shield around every N.S.A. site in the world, ensuring that the N.S.A. would be able to recover information from any of its locations, even if that site were completely destroyed in the event of war or another calamity. The N.S.A., in fact, was one of Dell’s most important and secretive clients.

Referred to within the agency as “OPS2A,” the N.S.A.’s main headquarters building at Fort Meade is an 11-story cube of steel and black glass. Set on 350 acres in the Maryland countryside, just off the Baltimore-Washington Parkway, it could easily be mistaken for a corporate office. It is surrounded by satellite buildings and a parking lot for 18,000 vehicles. Guard posts, many protected by hydraulic barriers, dot the perimeter and are manned by armed N.S.A. police. With 35,000 employees and a $10.5 billion budget—that was a secret until Snowden leaked it—the N.S.A. is the largest and most sophisticated eavesdropping operation in the world. Officially founded in 1952, the agency had its genesis in the effort to decrypt German and Japanese codes during World War II. Whereas the C.I.A.’s focus is on gathering intelligence involving human beings—“HUMINT”—the N.S.A. is the code-breaking, code-making, machine-and-computer outfit, specializing in what is known as signals intelligence, or “SIGINT.” It is the largest employer of mathematicians in the country, and possibly the world. “At the N.S.A.,” one former top official says, “an extrovert is someone who looks at your shoes when he talks to you.”

For decades the N.S.A. was the C.I.A.’s shadowy, little-noticed cousin, its contributions to national security barely known outside the intelligence community. Like the C.I.A., the agency suffered something of an identity crisis when the Cold War ended, only finding its new mission in the “War on Terror” that followed 9/11. It responded with such operations as ThinThread, Trailblazer, Prism, Turbulence, Muscular, and others with similarly ominous-sounding names. In various ways they were all giant electronic dragnets, sucking up e-mails, phone-call information, cell-location data, and other communications records.

In part, says Bruce Schneier, a leading security technologist and cryptographer who acted as a technical consultant to The Guardian on some of its Snowden stories, the N.S.A.’s “collect it all” mentality stemmed from unrealistic expectations in the wake of 9/11. “If you give the intel community the impossible mission of ‘never again,’ ” Schneier says, “the only way you can be sure you know that that thing won’t happen is to know everything that does happen.”

It all comes down to the nature of the modern threat. “We used to collect Soviet radio transmissions from Strategic Rocket Forces in Moscow,” Michael Hayden explains. “We were looking for words of interest like ‘launch.’ There isn’t a civil libertarian alive that gave a damn that we were doing that.” But when you start looking for information pertaining to terrorists and their targets, the grid of search options is almost infinite. “If I’m going to do what I used to do for you, I have to be on that grid. And I’m going to be bumping into your Gmail. I didn’t decide to bump into your Gmail. I didn’t rub my hands together and go, ‘Eeeexcellent.’ [But] I have to be where the signals are.”

The signals today are everywhere, and the N.S.A. has long believed the public has no right to keep them private. When public encryption technology first became available, in the 1970s, the N.S.A.’s director, Bobby Inman, wanted to make it a government monopoly, the way nuclear weapons are. In 1991, the mass-market encryption software program called Pretty Good Privacy, or P.G.P., was developed. The tool was so revolutionary that its creator was investigated by the U.S. government for violating U.S. export regulations—“arms-trafficking”—when the technology became available overseas. Alarmed that widespread public encryption would limit law enforcement’s ability to catch criminals, the N.S.A. proposed that an encryption chip be installed in any newly manufactured telephone, pager, or other electronic device, to give the government potential access. That idea went nowhere, but the agency then pursued opportunities to insert the same kind of “back doors” into encrypted platforms through subterfuge.

There were attempts by Congress to limit the N.S.A.’s new surveillance programs, but, as would emerge after Snowden’s disclosures, there was a lot that officials on the Hill didn’t know. Within the N.S.A., this conflict was playing out with the emergence of several earlier whistle-blowers. One of the first was William Binney, an N.S.A. technical director of geopolitical and military analysis, considered by some to be one of the best cryptography analysts in history. A 32-year N.S.A. veteran, he was an architect of ThinThread, a major dragnet program. But he became outraged when, on orders from the Bush White House, the N.S.A. deactivated the ThinThread privacy-control filters that prevented spying on Americans. Since federal law prohibits monitoring domestic communications without a warrant, he and other top officials, including senior analyst J. Kirk Wiebe, complained to Congress, to the Department of Defense inspector general, and even reportedly to a Supreme Court justice, but to no avail.

In 2007, F.B.I. agents burst into Binney’s home in Severn, Maryland, dragged him out of the shower, and held a gun to his head, while his family watched. The agents said they were hunting for the person who had leaked information about the government’s secret warrantless-wiretapping program to The New York Times.

Thomas Drake was another top N.S.A. official who had turned on the agency. Drake, after complaining formally to the N.S.A. and other government agencies, had leaked information about waste, fraud, and abuse at the N.S.A. to the Baltimore Sun, and this resulted in his being charged with violating the Espionage Act of 1917. The government’s case collapsed, but in the process Drake’s life was devastated: he lost his job, his security clearance, and his career. Today, he works at an Apple Store in Maryland.

Snowden wasn’t employed directly by the N.S.A.—he worked for its contractors, first Dell and then Booz Allen Hamilton. Like IBM, Boeing, Raytheon, and others, they receive multi-billion-dollar government contracts to provide everything an agency could need, from security guards and maintenance staff to satellites and supercomputers. Many of the contractors who service the N.S.A. are clustered in a set of sleek glass-and-steel buildings in a wooded area directly across from Route 295—and linked to the N.S.A. by a private road that passes beneath the highway. It’s called, fittingly, Connector Road.

“The culture of the contractors is one of the huge elephants in the room,” says Drake. “Because 9/11 just opened up the floodgates. We have always had contractors in the government. We’ve even had contractors in intelligence, but historically it tended to be much more circumscribed…. What were historically considered government functions only are essentially being outsourced, contracted, to private industry, who are focused on how much money they can make, on shares, on revenue streams. It’s a profit center.”

At the N.S.A., even the management of critical computer systems is outsourced to private industry—a very risky move, says William Binney. By giving away so much power, by allowing that kind of contract, “they are building in this access,” he says. “So when you do that kind of thing, now you are putting the family jewels out there with the contractors.”

Certainly Snowden saw himself as a highly principled individual, especially with regard to those faults he found in the U.S. intelligence community. His feelings appear only to have grown stronger while working for Dell in Japan. When asked later by The Guardian how his views had evolved over time, he responded, “When you are in positions of privileged access … you see things that may be disturbing,” adding, “Over time, that awareness of wrongdoing sort of builds up.”

A turning point seems to have occurred in May 2010, when Bradley Manning, an army private, was arrested in Iraq for releasing what was then the largest-ever trove of confidential government documents to WikiLeaks, the organization Julian Assange founded that has served as a clearinghouse for government secrets. The trove included some 250,000 State Department cables, a half-million pages of army reports, and chilling videos of U.S. air strikes in Iraq and Afghanistan in which civilians and journalists were killed. Snowden has said he was influenced by Manning’s subsequent ordeal at the hands of U.S. authorities—Manning was convicted of espionage and sentenced to 35 years in prison—which made him wary of similar treatment for himself.

In the summer of 2010, Dell promoted him to focus on clients other than the N.S.A., and he was eventually transferred back to Maryland, where he led a team of experts in designing cloud-computing platforms and supercomputers for breaking passwords. There he lived with his girlfriend, Lindsay Mills. Friends have described Mills, an avid amateur photographer and dancer, as a free spirit—extroverted, garrulous, and sweet. Two years younger than Snowden—she called him “E”—Mills had grown up an only child in Laurel, Maryland, another bedroom community popular with N.S.A. employees. She and Snowden had met a few years before, after she graduated from the Maryland Institute College of Art.

Attractive, blue-eyed, with long dark-blond hair, Mills was an inveterate user of social media. She blogged about her daily life in “L’s Journey” and regularly posted to her Instagram and Twitter feeds photos of herself in various stages of undress. Her exhibitionism would fascinate people later, but Snowden seemed oddly unaware of it. When an acquaintance referred to Mills as “your hot girlfriend,” Snowden replied primly, “My girlfriend is beautiful.”

Back in the U.S., Snowden was assigned a new job at Dell, as a high-level systems administrator—or “sysadmin”—at an N.S.A. facility in Hawaii. Much of what is known of his life during the year he spent there, from April 2012 to May 2013, comes via Mills’s Internet postings. “Trying to avoid the changes coming my way,” she wrote in March 2012 in a post accompanied by a nude photo of herself, sitting on a bed, covering herself and her face. That month, while she stayed behind in Maryland to pack, Snowden left for Hawaii. She arrived in June and they rented a house in Waipahu, a suburb 20 minutes northwest of downtown Honolulu. The house, in a sprawling development of apartment complexes and middle-class homes called Royal Kunia, is a light-blue bungalow with a pitched roof on a corner of Eleu Street, a residential lane jam-packed with small homes and lined, off-campus style, with dozens of cars and pickup trucks. None of the neighbors who later spoke to the press seemed to have had much to do with the young couple, but they thought them pleasant and neat.

In his new job, Snowden worked at the N.S.A.’s Kunia Regional Security Operations Center (known as “the Tunnel,” because it’s underground). It was a 10-minute drive north, up a two-lane road that snakes through sugarcane fields. The Kunia facility—or at least its guard shack and an entrance road, lined with orange barriers—can be seen behind high wire fences in a military complex that includes Wheeler Army Airfield and a naval security group. There are no signs to mark the N.S.A. facility, only a series of small fence markers that read, “WARNING. Restricted area. Keep out.”

Analysts at Kunia are said to focus on the electronic monitoring of China and North Korea. According to the N.S.A., Snowden had two jobs at Kunia. One was dealing with computer problems and questions from the staff. The other, as a sysadmin, was a kind of electronic-maintenance job in which, to aid in troubleshooting the facility’s computers and software, he was given wide-ranging access to the N.S.A.’s computers.

Snowden moved smoothly into his new job, where he made friends and impressed supervisors. A co-worker who came forward in an anonymous e-mail sent to Forbes last fall wrote that Snowden was considered a genius at computers, if a trifle eccentric. There was perhaps a clue to Snowden’s mental evolution in his dress. The Kunia facility was chilly, and the sweatshirt Snowden wore most days was sold by the Electronic Frontier Foundation, whose motto is “Defending your rights in the digital world.” According to the foundation, “the seal on the back features a red-eyed eagle using his talons to illegally plug into the nation’s telecommunications system with the help of telecom giant AT&T.” At Kunia, Snowden would later claim in a statement to the European Parliament, he spoke to more than 10 officials of his concerns about overreaching government surveillance, “none of whom took any action to address them,” he wrote. “Everyone in the intelligence community is aware of what happens to people who report concerns about unlawful but authorized operations.” But, according to Rick Ledgett, the N.S.A.’s deputy director who would lead the internal investigation of Snowden’s leaks, Snowden made no formal complaints. And if he complained personally to anyone, Ledgett says, they have not acknowledged it.

Snowden replies: “The N.S.A. at this point not only knows I raised complaints, but that there is evidence that I made my concerns known to the N.S.A.’s lawyers, because I did some of it through e-mail. I directly challenge the N.S.A. to deny that I contacted N.S.A. oversight and compliance bodies directly via e-mail and that I specifically expressed concerns about their suspect interpretation of the law, and I welcome members of Congress to request a written answer to this question [from the N.S.A.].”

In today’s electronic bureaucracies, both government and corporate, a sysadmin operates within fairly loose guidelines; like a motorcycle rider, he is free to roam far and wide, but only as long as he stays in his own lane. Later, after Snowden went public, N.S.A. experts studying his activities could see that, almost from his first weeks on the job, he had not only left his own lane but driven off the road entirely, zinging through open fields and peering into empty mansions. “He really went across policy lines and all kinds of things that he really shouldn’t have been able to get into as a sysadmin,” says William Binney.

Looking at what Snowden was able to do, Jeff Moss, the founder of the hacking conference DefCon and one of the country’s most prominent information-security experts, described the reaction of his peers around the world as one of widespread shock and surprise that the N.S.A.’s systems were so vulnerable to infiltration. “It’s enough to make you think offense gets all the money, and nobody really gets much for defense,” Moss says. “I think everybody assumed because of all the movies we’ve watched—like Enemy of the State—and all the experience with Soviet-era moles, that there were probably good controls.”

Only recently has the N.S.A. disclosed how Snowden could have had such wide-ranging access: he had been given a special assignment to copy millions of files from the central N.S.A. computers on the mainland onto servers in Hawaii, “building up stockpiles of data there that the island could use,” says Ledgett, in the event of a power outage or a cyber-attack. In retrospect, it seems astounding that a single person—and an outside contractor at that—would be given such power to root through the country’s national intelligence archives, but he was, according to the N.S.A. itself. The unique assignment was made necessary by Hawaii’s geographical remoteness. “Because Hawaii’s at the end of a lot of long, thin communication pipes, if there’s an outage, they’re sort of on their own,” says Ledgett. “And so he was moving copies of that data there for them, which was perfect cover for stealing the data.”

It was that summer of 2012, Ledgett says, when Snowden made his first illegal downloads. According to the N.S.A., one of those documents was the agency’s technical employment test, with the answer sheet. Snowden later took the test, and “aced it,” according to Mike McConnell, a former director of the N.S.A. and now the vice chairman of Booz Allen. Sometime in the fall of 2012, Snowden allegedly applied for a job at the N.S.A., got it, and then turned it down because he wanted a higher rank. “They offered him a position, and he said, ‘No, no, I don’t want to be a G.S.-13. I want to be an S.E.S.,’ a much higher rank,” McConnell told The Wall Street Journal. According to this account, when the N.S.A. rebuffed Snowden, “that’s when he turned.”

“Of course I didn’t cheat on the exam, although I’d argue being able to hack a hacking examination probably makes you more, not less, qualified for the job,” says Snowden. “This is just another artifact of a failed investigation, and I’m not sure why they trumpet it.” Snowden says he turned down the job offer because he didn’t want that particular position. “A Booz Allen executive wouldn’t be in a position to know about N.S.A.’s internal hiring. I imagine he’s trying to do an unrequested favor for the N.S.A. in hopes they won’t ask Congress to bar Booz from bidding on future N.S.A. contracts.”

If Snowden was then experiencing some kind of mental turmoil, his new home life certainly wasn’t helping things. A few weeks after Mills arrived, she tweeted, “The universe is telling me something and I’m pretty sure it’s saying ‘get out.’ ” In July she blogged, “For those that have forgotten I moved to Hawaii to continue my relationship with E. It has been an emotional roller coaster since I stepped off the plane.”

Mid-October, Mills blogged, was a time of “heavy conversations”; at one point, she complained of “stress paralysis.” She had been taking acrobatic- and pole-dancing classes in Honolulu and had managed to make friends there. At one point she finally got Snowden out of the house to meet them. Until then, she blogged, he had made himself so scarce people “weren’t quite sure E. existed.”

Around Thanksgiving, Mills returned to Maryland for a visit. She was still away on Saturday, December 1, 2012, when Snowden sat down with his laptop and tapped out his first message to Glenn Greenwald.

Greenwald was born in New York City to working-class Jewish parents and grew up outside of Orlando, Florida. An important influence appears to have been his grandfather, a Florida city councilman who ran for office on a populist ticket and fought for the rights of poor homeowners against powerful land developers. After his parents split, his mother took a job as a cashier at McDonald’s. Being a gay teenager in the mid-80s brought stigma and opprobrium, but instead of crumbling under the weight of cultural disapproval, Greenwald decided, according to The Advocate, “You’re not going to tell me that I’m wrong. I’m going to show you that your actions are wrong,” an attitude that seems to have stuck with him. He studied philosophy at George Washington University and graduated from N.Y.U.’s law school in 1994, then got a job at the venerable New York firm of Wachtell, Lipton, Rosen & Katz, selecting it out of about a dozen job offers because it came with civil-union benefits. After 18 months, at age 28, Greenwald quit and started his own firm. There, alongside defamation and workers’-comp cases, he took on difficult First Amendment issues, defending neo-Nazis and other unpopular clients. Former colleagues describe his fierce work ethic.

On the side, in 2002, according to BuzzFeed, he started a consulting company, Master Notions LLC, with his friend Jason Buchtel, a Los Angeles film producer. The company had an entertainment arm that operated an online retailer called “StudMall,” for sexually explicit gay DVDs. Greenwald has said that, while he has no objection to pornography, he was simply the company’s legal consultant. After he was bought out of the business and he and his longtime boyfriend had broken up, Greenwald decided to take a two-month vacation in Brazil. There, on his second day, while on the beach, he met a 19-year-old Brazilian, David Miranda, fell in love, decided to stay, and began to wind down his legal practice.

In October 2005, Greenwald started a blog called Unclaimed Territory, just two months before the world learned, in a groundbreaking story in The New York Times, about the warrantless wiretapping of Americans’ phone calls after 9/11. It was red meat for Greenwald. “Bush defenders,” he wrote at the time, “are now at the point where, to defend the President, they are literally advocating that preserving privacy against the Government is unnecessary, worthless and even dangerous.”

Unclaimed Territory was soon being cited in mainstream online magazines such as Slate, and two years later, in 2007, Greenwald was hired to write a regular column for Salon.

When Janine Gibson, The Guardian’s U.S. editor, approached Greenwald about a job with the paper, he was intrigued but didn’t want to give up the million-plus audience he had built at Salon. In the end he agreed to write for The Guardian with the same deal he had at Salon: his columns would be edited solely for legal and journalistic concerns. Alan Rusbridger, the paper’s editor, says Greenwald “came with a community of his own readers. He wanted his own rules.”

When Snowden’s initial exchanges with Greenwald didn’t go anywhere, he turned to Laura Poitras. Greenwald had published a column in Salon about Poitras, whose documentary My Country, My Country, about the American occupation of Iraq, was nominated for an Academy Award in 2007. Snowden had read the column, and it helped inspire him to reach out to her.

Poitras had grown up outside Boston and, after high school, moved to San Francisco, where she studied film at the San Francisco Art Institute. In 2004, for My Country, My Country, she went to Iraq for more than eight months and embedded with the U.S. military during the Iraqi elections. She spent much of her time with Dr. Riyadh al-Adhadh, an Iraqi medical doctor and Sunni political candidate. One day in November 2004, she was filming in a neighborhood where, the day before, Iraqi and U.S. military had raided a mosque during Friday prayer, and four people were killed. The next day, violence erupted in the neighborhood, and Poitras, who was filming nearby, captured some of it on video. An American National Guardsman was killed. American soldiers speculated that Poitras, who was seen on the roof of a nearby building that day, had known about the attack, though no evidence has ever been produced to support this claim. Poitras, who has never been questioned by anyone in the U.S. military about the incident, told The New York Times that “any suggestion I knew about an attack is false.” Two years later, she started being routinely detained by immigration officials.

All through that winter and spring, there had been no sense of an impending crisis at the blue house on Eleu Street. February 17 had been Mills’s 28th birthday. A week later she and Snowden went snorkeling. “Water and love dominated the weekend,” Mills tweeted, blissfully unaware of the changes Snowden was already planning for their lives. By that weekend, in fact, Snowden had decided to leave Dell. On the face of it he seemed to be trying to take a step up the intelligence ladder, shedding his job as a computer technician for actual espionage work; in fact, Snowden has indicated, he wanted access to more information he could download. Having passed on the N.S.A.’s job offer, he applied for and received a job at Booz Allen Hamilton, where he would move to the “cyber-security” side of the N.S.A., tracking and targeting threats to the country’s information infrastructure. Booz is a consulting company, controlled by the well-connected Washington investment firm the Carlyle Group. Nearly all of its $5.8 billion in 2013 revenues were derived from federal contracts—with $1.3 billion coming from intelligence work alone. Snowden was to work at Booz as a “target” or “infrastructure” analyst; he would be paid $122,000 a year plus benefits and would have access to a whole new range of information. “His job was to look at cyber-adversaries,” says Ledgett, “people who were exploiting U.S. communications or U.S. computer networks. And his job was to pursue them as targets and try to figure out what they were doing.” According to Snowden, the job was a gold mine of new information. “My position with Booz,” he said later, “granted me access to lists of machines all over the world [that] the NSA hacked.”

On March 30, Snowden flew back to the mainland, where he spent two weeks at Fort Meade training for his new job. He returned to Hawaii on April 13 and the next day picked up keys to a new rental home. (Hoping to sell the house on Eleu Street, the landlord had declined to extend the lease.) Mills posted to Instagram a photo of the two of them, stretched out on the carpet in their new living room. Lying on his side, Snowden wears black jeans and a purple T-shirt. His glasses are off, and he is looking away from the camera. Mills is sprawled on her back in a sapphire-blue dress. Both are barefoot. “Carpet dancing,” she wrote.

In early May, Snowden asked Poitras to forward a message to Barton Gellman, who had been communicating with her about her source since February. A Princeton graduate and Rhodes scholar who had spent 21 years reporting for The Washington Post, Gellman, while an aggressive reporter, was as reserved as Greenwald was outspoken. He had written a best-selling book, Angler, on Vice President Dick Cheney and his role in expanding the government’s surveillance powers, among other things.

Calling himself Verax, Snowden described the documents to Gellman, adding, “I understand I will be made to suffer for my actions, and that the return of this information to the public marks my end.” He warned that even a journalist in possession of the material was in danger. “The U.S. intel community,” he told Gellman, “will most certainly kill you if they think you are the single point of failure that could stop this disclosure and make them the sole owner of the information.” On May 16, Snowden contacted Gellman directly, and the two communicated steadily for the rest of the month. Snowden appeared resigned to his fate. “Perhaps I am naive,” he wrote, “but I believe that at this point in history, the greatest danger to our freedom and way of life comes from the reasonable fear of omniscient State powers kept in check by nothing more than policy documents.” He said he felt the peril was so great, “I have risked my life and family for it.”

Snowden was deliberately juggling the three journalists and their outlets. Each one—Gellman, Poitras, and Greenwald—offered a decidedly different prospect. “He did not want to be pre-empted,” Gellman says, referring to the government’s stopping publication. “That would have been his worst case. This, I think, does help explain why he had multiple outlets. He didn’t know whether any of us would be there ultimately or our news agencies wouldn’t go for it, or someone would come and take the documents from us, or whatever. And you can see what a meticulous planner he is from everything that is out now.” Snowden explains that approaching three journalists was his own system of “checks and balances.”

By Wednesday, May 15, Snowden had almost all of his documents ready. Even today, investigators are not sure how many, or exactly which ones, he took. They say that he had access to an astounding 1.7 million documents, and they estimate he eventually gave Greenwald and Poitras 50,000 to 200,000, most of which he had gotten while at Dell.

During his short time at Booz, Snowden was downloading documents until the last minute. In late April, for instance, he discovered a court order granting the N.S.A. access to certain phone-call information at Verizon, the giant telecom company. The order, signed April 25 and entered into the N.S.A. computer system April 29, touched on a special interest of Snowden’s: the issue of legal standing—the fact that lawsuits against the government on surveillance issues kept getting thrown out of court because no one could prove they were specifically being surveilled.

On Friday, May 17, Mills left for a week of sailing with friends. Snowden told her he was going on a business trip and probably wouldn’t be home when she returned. He told his bosses at Booz Allen that he needed to take a medical leave because of his epilepsy. He downloaded the last of his documents from the N.S.A. server, loaded them onto one last thumb drive, and left work.

The next day he walked into Honolulu International Airport, alone.

He arrived at Hong Kong’s Chek Lap Kok airport and took the half-hour cab ride to his destination: Kowloon, the teeming Oakland to Hong Kong’s San Francisco. The hotel he had booked, the Mira, was a deluxe lodging attached to an urban mall on busy Nathan Road. At the front desk, Snowden handed over his personal credit card. “I used a personal credit card so the government could immediately verify that I was entirely self-financed, independent, and had, over time, withdrawn enough financial resources to survive on my own for years without anyone’s assistance,” Snowden says. “My hope was that avoiding ambiguity would prevent spy accusations and create more room for reasonable debate. Unfortunately, a few of the less responsible members of Congress embraced the spy charges for political reasons, as they still do to this day. But I don’t think it was a bad idea, because even if they won’t say it in public, intelligence-community officials are regularly confirming to journalists off the record that they know with a certainty that I am not an agent of any foreign government.”

Once the credit card’s numbers entered the Mira’s system, he knew, it wouldn’t be hard for anyone in law enforcement to find him.

In his Mira hotel room, a small space dominated by the bed, he closed the curtains and set up shop. He was intent on wooing all three of his target journalists, the better, he has acknowledged, to get one to take the bait. He had kept in daily contact with Bart Gellman, and by Thursday, May 24, he had sent him 41 slides of Prism documents, and a demand that the Post publish them within 72 hours. (Snowden now says the request was a “test” to “establish how much I could trust him in a very short time, under very tight situational constraints.” Gellman notes that, “Over time I would say we’ve earned each other’s confidence. We kept our word to one another.”) It was in the details of this request, Gellman points out, that Snowden disclosed the hand he was playing: to reveal his identity and seek political asylum elsewhere. The slides would be his calling card: if the Post reprinted them, it would have to agree to reproduce the unique cryptographic signature on them. Because the signature would be the same on both Snowden’s and the *Post’*s slides, it would serve as concrete evidence that Snowden had leaked them, a fact he could then use as support for an asylum request. According to a Washington Post article Gellman later wrote, Snowden thought he would apply to Iceland, which has strong Internet and press freedoms. “The strength of the reaction’’ to his disclosures, Snowden said, “will determine how choosy I can be.’’

It was during these e-mail exchanges, Gellman confirms, that Snowden revealed his identity to him and asked to meet in Hong Kong. But each of Snowden’s disclosures forced Gellman to cross an additional threshold, and raised thorny questions about the relationship between a journalist and a source. “First of all, I now know the identity, [so] I now am responsible for protecting the identity of someone for whom the stakes are very, very high,” Gellman recalls. “He thinks it’s possible that his life is at risk. I can’t say I know he’s wrong about that—it’s plausible. He certainly knows that his freedom is at risk. He certainly knows that the materials under some circumstances could be at risk (that is, that someone could steal them)—you know, in the very earliest days. So I’ve got that responsibility.

“Now I also know he’s out of the country and in the jurisdiction of a country that’s unfriendly to the United States, and I know that he wants to seek asylum. And I have to maintain the lines of what is a journalistic relationship or opt for something else. I can’t help him evade U.S. jurisdiction—I don’t want to, and I can’t. It’s not my job. It’s not the relationship. I am a journalist. I’m treating him as a confidential journalistic source, and I will respect those confidences to the limits of my ability. And nothing more than that.” Despite the high-wattage nature of the story, Gellman could not press ahead on Snowden’s timetable, something that clearly frustrated Snowden, but he continued to work on the story.

Initially Snowden had no better luck with Glenn Greenwald. According to Luke Harding’s book, The Snowden Files, after months of having no direct contact with him, Snowden tried to reach Greenwald over a P.G.P.-encrypted channel. “I have been working with a friend of yours,” Snowden said, referring to Poitras. “We need to talk, urgently.” He added, “Can you come to Hong Kong?”

But Greenwald, who was finishing a book and couldn’t fathom what a security- agency person was doing in Hong Kong, didn’t respond. Snowden then tried Poitras, asking if she might persuade Greenwald to fly to Hong Kong “right now.” Poitras contacted Greenwald, who finally got back to Snowden. Even then, Greenwald was reluctant to travel so far until he knew more. “I would like some more substantial idea why I’m going,” he wrote Snowden, “and why this is worthwhile for me?” At which point Snowden replied, “I’m going to send you a few documents.”

It was later that week, on May 31, that Greenwald and Poitras went to The Guardian’s New York offices, in SoHo, and Ewen MacAskill was assigned to be the group’s overseer. The next day the uneasy trio—Greenwald, Poitras, and now MacAskill—boarded the long flight to Hong Kong.

On Monday morning, June 3, Greenwald and Poitras went to meet their shadowy source at the Mira, leaving MacAskill behind at the W hotel, where they were all staying. Snowden had said to meet outside a restaurant at the mall; he would be carrying a Rubik’s Cube. They arrived early; he wasn’t there. When they returned later, they saw him, a thin young man holding a Rubik’s Cube. According to Harding’s book, they followed the instructions that he had sent earlier.

“What time does the restaurant open?” Greenwald asked.

“At noon,” Snowden replied. “But don’t go there. The food sucks.”

Then Snowden glanced around. “Follow me,” he said.

Both Poitras and Greenwald were shocked by how young he was. They had expected someone middle-aged, someone who had spent years learning the things he knew. Could he be real?

In silence they followed him into the hotel lobby, then into an elevator and up to the 10th floor. The long hallway there, with its dim lighting and glass ceiling, seemed eerily appropriate, as if they were walking down a hall of mirrors. At Room 1014, Snowden inserted his keycard, and everyone stepped inside. They introduced themselves.

The room was cramped, and Snowden’s suitcase was on the floor, open, displaying the few clothes he had brought with him. Angler, Barton Gellman’s book on Dick Cheney, sat on a table under the mirror. Empty containers of take-out food cluttered a small desk. On the floor next to the door was a glass of water. And next to the glass was a napkin with a drop of soy sauce on it. This was an old spy trick to detect if an intruder had entered when the occupant was away. Anyone who opened the door would spill the glass of water, which would change the soy-sauce pattern.

Once inside, Poitras started filming almost immediately, positioning herself between two windows overlooking Kowloon Park, where children could be seen playing beneath the low clouds. The move was risky. It could have been too aggressive a step for a nervous source, but those who know Poitras say it was just a normal expression of her relentlessness and focus on her work. She and Greenwald spent much of that first day going over the documents Snowden had sent. They discussed Snowden’s background, and how he had come to his decision to leak this vast trove. The conversation took a philosophical turn, deploring the audacity of the N.S.A., with Poitras and Greenwald reveling in the proof of the government’s surveillance that had so far eluded them. Later, Greenwald told MacAskill, “Look, he’s young, but I think this guy’s credible.”

On Tuesday, Greenwald brought MacAskill to the Mira. Poitras herself had moved there from the W to be closer to Snowden. When the two men arrived, Snowden politely greeted MacAskill, then returned to sit on the bed. “My first reaction was relief that he was still there,” MacAskill says. He asked if he could record their conversation on his iPhone, at which Snowden recoiled. The N.S.A., he said, could overhear anything said on the phone and also use it to determine his location. Poitras offered to put it in the refrigerator in her room down the hall. Once the phone was gone, Greenwald and MacAskill sat on chairs by the window, with Poitras standing between them, filming. Snowden lay on the bed, propped up on pillows against the headboard.

While the others focused on documents, it was MacAskill’s job to observe Snowden, so he could relay to his editors whether he was credible. His first impressions of the slight young man in a white T-shirt and jeans were not encouraging, MacAskill admits. Listening to Snowden detail his background, MacAskill doubted every word he spoke. “At first I thought, This is just a kid—how can he know all these things?” he recalls. “A couple of times, when he was talking about his life, my heart sank. Because I thought … training to get into the Special Forces, it just sent the panic buttons going. The idea that he would have done all these things—C.I.A. employee in Geneva, being in Japan for the N.S.A., being in Hawaii. And yet, he looked about 23. And not having been to university. I mean, this can’t be true. This guy’s Walter Mitty.”

But at a certain point MacAskill’s doubts began to fade. There was just too much detail. Snowden provided his Social Security number, where he’d been to school, where he’d lived, details about his girlfriend and his parents, dates and places where he’d worked. He had printed pages and pages of his background. If he needed to get something off one of the laptops he had brought with him, he put a large blanket over his head and shoulders, one that obscured anyone else’s view of his screen and his keystrokes.

By day’s end, Greenwald and MacAskill had finished a draft of their first article—about the N.S.A.’s indiscriminate collection of Verizon customers’ phone records—which The Guardian planned to publish the next day.

On Monday, in New York, Gibson pulled the shades in her office and scrawled out a plan for their first story on a white dry-erase board: seek legal advice, approach White House, get draft of story from reporters in Hong Kong. On Wednesday, June 5, after MacAskill filed the draft, the reporter assigned to seek comments, Spencer Ackerman—it was actually his third day at The Guardian—telephoned Verizon. A P.R. person took the message. Later, that person called back, asking about the court order in a way that made it clear there was a match in Verizon’s files. “They called back and said, ‘What’s the name of the agency on the court order? And what is the date?’ … It was a bit like ‘Is it the pink one or the yellow one?’ ” Gibson recalls.

By midafternoon The Guardian still hadn’t gotten anywhere with the White House. Because Ackerman’s e-mail to Caitlin Hayden, the National Security Council spokesperson, didn’t include enough urgent detail, it took Hayden some time to return the call. When she did, she was shocked. That was the first indication to the White House that there was a leak, but at this stage it seemed to be just a single document. Ackerman told her the paper intended to publish a story based on a secret Foreign Intelligence Surveillance Act (FISA) court order. Their deadline was 4:30 P.M. Hayden scrambled to assemble a conference call among Janine Gibson, the deputy directors of the N.S.A. and the F.B.I., and the general counsel for the Director of National Intelligence.

When the call finally happened, at 5:15, Gibson described the document and the paper’s intention to publish that night. The government players on the line listened, astonished, according to one person on the call. The document, dated April 25, 2013, and stamped TOP SECRET, outlined the bulk collection of all of Verizon’s customers’ phone records for a period of 90 days. It was a renewal notice—that is, the renewal of a standing court order from the FISA court.

It was a circular conversation, in which the government men were unable to discuss the document, and The Guardian was unwilling to budge unless they outlined a specific security threat that would result from the document’s publication. Gibson pressed; she thought it was possible the government could have done this as a one-off to investigate the Boston Marathon bombing. But for anyone from the intelligence community to even acknowledge the existence of a classified document may be a crime. One man on the line said tersely, “I’m not in the habit of committing felonies.” Gibson, who had practiced her talking points and was steady, stood her ground. “I think you’ll find, madam,” he replied, “that we are much better positioned than you are to say what is a national-security risk.”

“No serious news organization would do this,” said another government voice on the call. To which Gibson replied, “I think you’ll find, sir, that we are much better positioned than you are to say what is a story.”

The call lasted 45 minutes.

When the journalists had come to Snowden’s room that morning, MacAskill sensed something was wrong. In those first two days Snowden’s demeanor had remained unchanged—cool, focused, professional, resigned to his fate. But now they found him angry, shaken, deeply distracted. When they asked what was wrong, he said the N.S.A. was looking for him.

According to intelligence sources, neither Booz Allen nor the N.S.A. yet knew that Snowden had taken classified documents. At this point he was simply missing. It’s believed his family contacted Booz Allen when they couldn’t reach him, setting off alarms. “I feel alone, lost, overwhelmed, and desperate for a reprieve from the bipolar nature of my current situation,” Mills wrote that Monday.

When Snowden was still missing on Tuesday, the N.S.A.’s efforts to find him intensified. On Wednesday, a Century 21 real-estate agent, Kerri Jo Heim, was at the bungalow on Eleu Street with a photographer, preparing for an open house. At one point she was surprised to see two people, one a uniformed policeman, approach the front door. “They just asked if I knew what had happened to the former tenant, and I said I didn’t know,” Heim recalls.

That morning at the Mira, Snowden “was emotional” and had been worrying about his girlfriend, MacAskill remembers. “He was still lying in bed. Just agitated.” Told of this, a person who knows Snowden well says, “Part of him is very naïve. I think he thought the world would see how fucked up what the N.S.A. was doing is and give him a part in a parade. I think he knew people would get mad, and charge him, but that the more that came out, the more people would say, ‘Hey, no.’ ”

That first Guardian story sent tremors through the N.S.A. Somewhere, it was clear, there had been a leak. But was it inside the N.S.A. or elsewhere? Verizon? A rogue congressional source? No one as yet had any sense of how serious this might be. “This data was coming in, but there was no context,” says one official. The Guardian gave them very little to go on.

The impact, however, became clear the next day, when Gellman called, seeking comment from the White House and the director of central intelligence for a Washington Post story based on what appeared to be a second batch of documents, those dealing with the Prism program. Gellman’s approach was direct and without embellishment. He e-mailed and called senior officials, saying, as he recalls, “This is one of those once-in-a-very-long-time kind of things. I have something important to talk to you about. It’s a document with this title, this author, this date. Why don’t you go get it and tell me how you want to proceed.”

By that point the N.S.A. had initiated an intensive search for the source of the leak, scanning every computer they thought relevant. “We had folks going through the networks, looking for the footprints,” Ledgett says.

According to Ledgett, it took 48 hours to identify the likely culprit: a Booz Allen contractor named Edward J. Snowden, the same Edward J. Snowden, he learned, who had been missing since Monday. It was the N.S.A.’s nightmare scenario.

In an odd confluence, both The Guardian and The Washington Post printed their Prism stories on the same day, Thursday, June 6. A sense of urgency pervaded the tiny hotel room as the week wore on and more Guardian stories appeared on Friday and Saturday. Everyone knew time was running out. On Thursday evening Greenwald had given a live interview on CNN, and the on-screen text identified him as being in Hong Kong. With Snowden using his personal credit card, it was only a matter of time before someone tracked him down. MacAskill thought about it every morning when they knocked on the door of Room 1014. “Almost every day we thought he wouldn’t be there,” he says. “We thought he would be apprehended. Whenever we met, we half expected the door to crash open and the C.I.A. or the police would come barging in.”

Once the first stories were published, Snowden wanted The Guardian to identify and interview him so he could state his motivations, to own his story. MacAskill repeatedly tried to talk him out of it. He had three sons around Snowden’s age and kept thinking what he would want any of them to do in such a situation: if Snowden went public, MacAskill knew, he would be throwing away everything he had ever known—his career, his girlfriend, probably his freedom. “I thought, This is a kid that’s going to prison for the rest of his life,” MacAskill recalls. “I kept saying, ‘Look, you should remain anonymous—the stories are just as good without you. As soon as your name comes out, your life is over.’ But he knew there would be inquiries at the N.S.A., and he didn’t want to put his colleagues through all that.”

On Thursday Poitras filmed an interview, eventually cutting it into a 12 1/2-minute video they planned to post to The Guardian’s Web site after the weekend. Greenwald, who handled the questioning, had persuaded Snowden to ditch his white T-shirt and put on a gray dress shirt.

By Sunday, June 9, they had finished writing all the stories they could without further research. MacAskill asked Snowden, as he had several times, what he planned to do next. “He said he intended to stay in Hong Kong and fight extradition,” MacAskill recalls. “I pressed him: did he have an exit plan, a Plan B? And he didn’t. He just didn’t have a clear plan. He just hadn’t thought beyond that point. I actually thought he would be O.K. Once the stories came out, they gave him a lot of cover. It was unlikely the C.I.A. would come to arrest him then.”

Snowden’s interview was scheduled to be posted on Monday in the early-morning hours, Hong Kong time. No one knew what would happen next. That evening, after saying their good-byes for the day, MacAskill realized that, despite all the filming, they had never taken a still photograph of Snowden. He returned to the Mira, and Snowden happily posed. “When I left I assumed I would see him in the morning,” he recalls. “I assumed he would be giving a press conference at some point on Monday.” MacAskill never saw him again.

That night everyone stayed up late, waiting for Snowden’s interview to go live on the Guardian Web site. The three journalists splayed themselves around Greenwald’s room at the W; Snowden remained alone at the Mira. Finally, at three A.M. Hong Kong time, it happened. The interview immediately went viral, ricocheting to media outlets and blogs around the world. “We got the response we fully expected,” MacAskill recalls. “The bubble just burst, and it went whoosh, and suddenly it was everywhere, on Twitter, all the media, everywhere.” Snowden chimed in from his computer. “He was really pleased,” MacAskill remembers. “He even made a few jokes.”

Later that morning, Greenwald and MacAskill emerged to find the W’s lobby filled with camera crews and reporters. The two journalists answered a few questions, then scurried off. In the meantime, one enterprising reporter managed to identify a lamp next to Snowden in a photo on the Guardian Web site as one of those at the Mira. At that moment, Poitras was filming Snowden in his room as he prepared to leave. He wouldn’t say where he was going. By the time the first reporters finally made it to the Mira, he had vanished.

Lindsay Mills soon did as well. (It was rumored she fled to the West Coast.) Her melodramatic final blog entry, filed that Monday, read, “As I type this on my tear-streaked keyboard, I’m reflecting on all the faces that have graced my path…. The ones I’ve held. The one I’ve grown to love the most. And the ones I never got to bid adieu. At the moment all I can feel is alone.” And on Twitter she wrote, before signing off, “I have lost my compass and find myself adrift in a sea of chaos. Goodbye my friends.” Mills being Mills, the Twitter entry linked to an Instagram photo of her wearing red panties and a white bra. She was seated cross-legged and holding a globe, with her back to the camera.

From the moment he left the Mira that Monday morning, Snowden became a pawn in an international game of chess. In the next few weeks an array of players would crowd around the board, including the U.S. Justice Department and numerous foreign governments, from American antagonists such as China and Russia to marginal aspirants such as Bolivia and Ecuador. Each had its own motives and strategy, though those motives and strategies were not always clear—with the notable exception of the White House, which wanted to arrest Snowden as a traitor.

Those first few days, as reporters raced around Hong Kong in search of Snowden, much of the media turned its focus to Iceland. In the final paragraphs of the Guardian story that Monday morning, Snowden had volunteered, somewhat airily, that he might seek asylum there, noting their commitment to Internet freedom. The capital, Reykjavík, was home to several notable transparency activists, including a onetime television reporter named Kristinn Hrafnsson, the official spokesman and de facto No. 2 of WikiLeaks.

“He mentioned Iceland specifically,” recalls Hrafnsson, a tall, white-haired man possessed of such icy Nordic cool some reporters call him Lurch. “So I thought we needed to reach out.” Hrafnsson brokered a conversation with several attorneys in Hong Kong who were working on Snowden’s behalf. “That led to a discussion,” Hrafnsson goes on, “in which I was asked to serve as intermediary to begin carrying messages to the Icelandic authorities.”

In the meantime, the prime minister’s office was besieged by the international press corps. “We started getting calls from the media on Monday, and it just never stopped,” remembers an Icelandic official involved in the situation. “We were caught totally off guard. We had heard nothing from Snowden, nothing from WikiLeaks, nothing from anyone. We kept saying, ‘We’ve received no formal requests from anyone.’ We were just reading the newspapers like everyone else. But we had to be very careful. There was immense support for Snowden here. It was like 50-50. A lot of people thought of him as a hero.”

Hrafnsson “called me, and he called the Interior Ministry,” the official recalls, “and he got the same message from both of us, the same thing we had been telling the media, that [Snowden] would have to be in Iceland to apply for asylum. What he was fishing for was giving Snowden a political ‘free pass,’ like a passport.”

“I was disappointed,” Hrafnsson admits. “I thought this was a sorry response and an incredible lack of vision.” Trying to force the issue, he hurriedly wrote an op-ed piece for Fréttabladid, Iceland’s largest newspaper, critical of the government in outlining what was going on. “That’s Kristinn for you,” the official says with a sigh. “It was the only thing he could do at that point.”

Hrafnsson’s article struck a nerve, and a public outcry ensued. Out at Keflavík, Iceland’s international airport, reporters from London and New York began filing off planes and heading into the capital. Many of the Icelanders they interviewed said Snowden should be granted asylum. But Hrafnsson’s article, while generating a good deal of public support, essentially killed any chance of that actually happening. “The government, because of what Kristinn wrote, they would not help Snowden,” says Birgitta Jónsdóttir, a onetime WikiLeaks official who now heads a left-wing Icelandic political party. “It was quite counterproductive. He did this as I was trying to talk to the Interior Ministry for this same case. He kicked them all with one foot while asking for that kind of support.”

Even though the government was not considering granting asylum, says the Icelandic official, “now we had to prepare that Snowden would come. We actually thought that might happen, that he would just show up one morning at Keflavík. That was the nightmare scenario. That was also when we started hearing from the U.S. Embassy. The tone of the message was very professional, not threatening in any way. But still, we really feared Snowden would show up here. It would have been very hard to just arrest him and send him to the U.S. But it would have been very hard not to and still get along with the U.S.”

Even as his aide-de-camp grappled with the Icelandic government, Julian Assange was desperately looking to be a player in the Snowden affair. Assange and his organization, founded back in 2006, were on their last legs. The WikiLeaks Web site, once used by Bradley Manning and other whistle-blowers, struggled to continue operating due to legal concerns and a lack of money. Assange himself, the target of a sexual-assault investigation in Sweden, had been marooned inside the Ecuadoran Embassy in London for more than a year. The U.S. Justice Department was investigating whether he had illegally solicited material from Manning. Now came the largest, most important leak of confidential documents in history, and Assange found himself on the outside looking in.

“Assange, like an ageing movie star, was a little put out by the global superstardom of Snowden,” Andrew O’Hagan would write in the London Review of Books, in his account of working with Assange on a memoir. “He has always cared too much about the fame and too much about the credit.” Another source says of his reaction to Snowden’s prominence, “This is humiliating for him.”

Snowden himself points out that his own views don’t always coincide with Assange’s: “We don’t share identical politics.” For one thing, Snowden believes that governments have a legitimate interest in security. “I am not anti-secrecy,” he says. “I’m pro-accountability. I’ve made many statements indicating both the importance of secrecy and spying, and my support for the working-level people at the N.S.A. and other agencies. It’s the senior officials you have to watch out for.” But there is much that he admires about WikiLeaks. “They run toward the risks everyone else runs away from,” Snowden says. “No other publisher in the world is prepared to commit to protecting sources—even other journalists’ sources—the way WikiLeaks is.”

During a telephone press conference Assange bragged about assisting Snowden’s legal team in Hong Kong. For the moment, though, all he could do was talk. To do more, he needed someone at Snowden’s side. Unfortunately for him, WikiLeaks had no central office or permanent employees; it had only backers and volunteers, among the most eager of whom was a young woman named Sarah Harrison. She had joined WikiLeaks as an intern three years earlier and was known around London as Assange’s girlfriend. Harrison had been traveling in Australia but immediately agreed to fly to Hong Kong, where, Assange later announced (possibly with an eye toward avoiding legal prosecution), she would serve as Snowden’s “legal researcher”—never mind that she had no formal legal training. Snowden, however, would come to appreciate the help and support that Harrison provided. “Sarah is extraordinarily courageous,” he says. “She’s the kind of person who will walk through hell to do the right thing, and I think it’s fair to say that with the unprecedented and at times unlawful manhunt we saw last year, she got her chance.”

By mid-June, Harrison had arrived in Hong Kong and made contact with him. Once Harrison was in place, Assange began working on the second stage of his plan: finding a country that would grant Snowden asylum. The natural refuge was his own protector, Ecuador, so Assange began consulting with the embassy’s legal attaché, his friend Fidel Narváez, attempting to craft some kind of document that would grant Snowden safe passage to that country.

Snowden, meanwhile, remained in hiding in Hong Kong. Some believe he was at an out-of-the-way house arranged by the three attorneys he had retained who now oversaw his fate: Albert Ho, a prominent local legislator and fixer; his young associate, Jonathan Man; and a canny Canadian-born specialist in extradition matters, Robert Tibbo. None will discuss their roles today, but their two-pronged strategy was clear to everyone in the burgeoning community of human-rights activists in Hong Kong. Behind the scenes, they needed to feel out government officials to see how Snowden’s situation was viewed. That would take time, so the trio’s top priority was rallying public support, to make it harder for the Chinese to hand over Snowden to the Americans. “The thinking was, if we could get some attention on the actual person, we could offer him some protection,” recalls Tom Grundy, a Hong Kong activist who became involved in the efforts to publicize Snowden’s situation. “We had to raise his profile. That way maybe he couldn’t just be ‘disappeared’ off the street, we thought.”

The first step in their public-relations campaign was reaching out to a local reporter, Lana Lam, of the English-language South China Morning Post. On June 12, Snowden gave Lam an interview in which he claimed that the U.S. hacked computers all over China.

By Friday, June 21, it was clear the situation was approaching an endgame. Snowden’s attorneys had made little headway with the Hong Kong government, which had held numerous internal meetings about the situation, without including Snowden’s lawyers. The problem, it turned out, was Albert Ho, who had long agitated for Hong Kong to enjoy a full and open democracy—the government didn’t trust him. Instead, according to The New York Times, an intermediary from the government had managed to get a message to Snowden directly.

The message reportedly startled Snowden. If the U.S. requested his extradition, the Hong Kong government could not predict how a local judge would view his case. But it was entirely possible he would need to wait in jail until they figured it out. What especially bothered Snowden, his lawyers would say later, was the intermediary’s assertion that he wouldn’t be able to use a computer while in custody. The one claim that offered Snowden hope was a suggestion that the government would welcome his departure from Hong Kong. (This version of events has been disputed by those close to Snowden.) But it was at that point, it appears, that he made his decision. He would go with Assange’s plan to head to Ecuador. He and Harrison booked the first leg of the trip—an Aeroflot flight to Moscow that left the next night, Saturday, June 22. From Moscow they would fly on through Havana and be in Quito in two days.

But by that same Friday night the situation again changed dramatically. That evening the news broke that the US government had filed a criminal complaint against Snowden charging him with espionage and had asked Hong Kong to detain him on a provisional arrest warrant. All three of Snowden’s attorneys convened at his hiding place to decide what to do. Ho brought a dinner of fried chicken, pizza, and Pepsi. Snowden, backed by Harrison, was determined to leave Hong Kong as quickly as possible. The lawyers appear to have counseled caution. It was always possible that the call from the “intermediary” was a trap. Welcoming Snowden’s departure didn’t necessarily mean he wouldn’t be arrested if he appeared at the airport.

Snowden asked the lawyers to make one last approach to the government, to see if they would guarantee him safe passage. All that Saturday they waited for some kind of response. Snowden decided to cancel his flight. Finally, at about six P.M., Ho would say later, he received an equivocal response from someone in the government. Reading between the lines, Ho guessed they would be safe going to the airport. Crossing their fingers, Snowden and Harrison made new reservations on a flight leaving Sunday.

The next morning, accompanied by one of his attorneys, they were driven to Chek Lap Kok airport. Snowden wore his gray shirt and backpack, glancing about nervously as they strode into the international terminal. According to The Washington Post, they noticed men following them, whom they assumed to be plainclothes policemen. But no one approached them as they headed into the security lines. The moment of truth came when Snowden presented his passport for inspection. The day before, the Americans had canceled it.

Spokesmen at the White House and the State Department would later claim they had told Hong Kong the passport was no longer good. Hong Kong authorities insist no one told them. Official Washington fired back that, in any event, Snowden should have been detained as a result of its extradition request. In Hong Kong, the justice minister would furrow his brow, tut-tutting about “irregularities” in the request. The U.S., he said, had demanded the detention of an “Edward James Snowden” in some documents. But his actual name was “Edward Joseph Snowden.” Hong Kong had asked for clarification, the minister insisted, but never heard back from Washington. As a result, Hong Kong had had no legal basis to detain Snowden.

The explanation, as just about everyone in Washington and Hong Kong knew, was the thinnest of subterfuges. “The Hong Kong authorities were happy that Snowden was leaving. They just wanted to wash their hands of the whole thing,” says Law Yuk-Kai, director of Hong Kong’s Human Rights Monitor. “It allowed them to avoid an embarrassing situation between the mainland authorities and the U.S.”

And so, that Sunday, Snowden and Sarah Harrison boarded Aeroflot Flight SU213 without incident. Snowden had his four laptops, but, he says, they had no government information on them and never did. He says he carried no documents. “I didn’t want to risk bringing them through Russia.” If all went well, they would be in Moscow by dinnertime.

At that point probably fewer than a dozen people knew the most wanted man in the world was aboard a flight winging its way over remotest Siberia. And yet, by the time Snowden and Harrison peered out their window at Moscow’s Sheremetyevo International Airport, a throng of reporters and cameramen were waiting. The New York Times actually live-blogged their arrival. Ever since, those involved have been pointing fingers over who leaked Snowden’s itinerary.

“Why was this made into a media situation before he was even safe?” Birgitta Jónsdóttir wonders. “Who said he was on the Moscow flight? Who? I’d like to know.” Jónsdóttir, like many others, believes it must have been Assange, or one of his acolytes, who leaked the news. “There was a massive mix-up somewhere, which was very serious,” she goes on. “I have to say, and this will surprise many people I know, but it was a massive mistake to include WikiLeaks in any of this. It didn’t help. It just made things worse. I mean, when you are making decisions on a person’s life, it must be done on solid ground. And this was out of control.” She makes a face. “I support WikiLeaks’ message,” she says, “but not its execution.”

Assange had, in fact, issued a celebratory tweet while Snowden was still in the air that afternoon, but it came only after journalists had already learned he was on the flight. The first to announce Snowden’s departure for Moscow appears to have been Lana Lam, of the South China Morning Post. Her story, which ran alongside a blurry photograph of a passenger in the departures area of the airport, was published at 3:31 P.M. Lam, unsurprisingly, won’t discuss the source of her information. That the leak came in Hong Kong suggests that a source in the government was behind it. The first official announcement of Snowden’s departure did, in fact, come from the Hong Kong government, which that afternoon issued an unusual press release that pointedly did not say where Snowden was heading.

At Sheremetyevo, meanwhile, the crowd of journalists waited anxiously for Snowden to appear outside customs. They waited for a full hour, then another, and another. Finally word spread that he and Harrison were booked onto an Aeroflot flight to Havana, leaving at 2:05 the next afternoon. They had seats 17A and 17C. Several journalists immediately purchased tickets of their own.

The next day two dozen or so other journalists managed to make it into the boarding area, until a group of Aeroflot attendants shooed them away. Everyone else filed onto the flight, craning their necks for any sign of Snowden. He hadn’t boarded yet. Finally, in the last minutes before departure, with still no sign of Snowden, a murmur spread among the journalists on the flight: “Ne uletayet, ne uletayet!”—Russian for “He’s not flying.” Snowden wasn’t coming, leaving a dozen journalists marooned on the flight, according to The Snowden Files. Max Seddon, then a foreign correspondent for the A.P., was left to post a forlorn photo of what might have been. “Standing next to Edward Snowden’s seat on flight to Cuba,” read the Twitter message above the picture of an empty seat. “He ain’t here.”

While Snowden was holed up, an N.S.A. delegation, led by General Keith Alexander, and the then director of the Threat Operations Center, Rick Ledgett, boarded a military jet to Hawaii to try to make sense of Snowden and the damage he had caused. For months after Snowden revealed his identity, it was hard to find anyone at the N.S.A. who would utter his name in public. This was to some extent a denial reaction, reflecting shock and embarrassment. There was also a sense of personal betrayal, says Ledgett, who adds, “It was like getting kicked in the stomach.

“It’s the national-security implications, which are, you know, immense,” he continues. “And it’s somebody who had one of these badges,” he says, fingering his own top-security-clearance badge, “who betrayed the organization…. You like to think that you have shared values, and you have shared reasons for being here, because it’s not the pay. So to realize the organization is harboring this person, who didn’t share those views, and then betrayed us that way … ” His voice trails off.

He and Alexander talked to Snowden’s superiors and co-workers and “retraced his footsteps, saw what he did, saw where he sat,” says Ledgett. To assess the threat of more Snowdens, they had to understand what made people like him tick. What had driven this 29-year-old to give up almost everything he had ever known, possibly forever?

Snowden has insisted it was all about principles, about a lone individual standing up to fight. “You can get up every day,” he told The Guardian, “go to work, you can collect your large paycheck for relatively little work against the public interest, and go to sleep at night after watching your shows. But if you realize that is the world you helped to create, and it’s going to get worse by the next generation and the next generation . . . ”

In the intelligence community, however, there is a starkly different point of view. “Snowden to me is just like the spies in the Cold War who went to work for the Russians because they believed ideologically,” says a former senior intelligence official. “Manning is clearly troubled psychologically and emotionally, but with Snowden you seem to have a true believer,” he says, “driven by the proposition that all information should be free.”

In counter-espionage there is a template for evaluating the psychological motivations of those who are likely to spy, to become double agents. The acronym is MICE, which stands for money, ideology, compromise or coercion, and ego. After the early, ideological Americans who spied for the Soviet Union, things devolved, experts say, as spies increasingly did it for the money and for ego reasons. For many of those who consider Snowden a traitor, he scores high on the ego motive. They cite the swagger in his Internet postings, the braggadocio of his public statements, including his claim to The Guardian that he had the power to wiretap anyone, “even the President, if I had a personal email.” (“Bullshit,” says Ledgett.) In Snowden’s Ars Technica posts, the former official argues, “you don’t get any sense of a struggle, any inner debate, or conflict, or concern … I think he is a narcissist, a lot like Rick Ames” (the 90s-era C.I.A. turncoat).

What no one, not even Snowden’s most vociferous critics, suggests, though, is that Snowden did it for money or personal gain. “There are some whistle-blowers out there who do want to be deified,” says Jesselyn Radack, one of Snowden’s lawyers and the national-security-and-human-rights director at the Government Accountability Project, which advocates for whistle-blowers. But whistle-blowing, especially from within the intelligence world, where there is virtually no protection from whistle-blower laws, is too traumatic, Radack says, for anyone to do it lightly, or for ego gratification only. Radack was herself a whistle-blower—a former Justice Department attorney, she was pushed out of her job after objecting internally to the torture and interrogation of John Walker Lindh, the 20-year-old American who was captured fighting with the Taliban in 2001. She later leaked the information to Newsweek. In the process, Radack went “through hell,” as she puts it. No law firm would hire her; the government blackballed her privately and pursued her legally; she was ostracized. Among the many “smears that whistle-blowers are subjected to: that they did it for vengeance, fame, profit, or self-aggrandization. People try to pathologize whistle-blowers,” says Radack. Some might be naïve, others hopelessly idealistic or moralistic, or intense, but what all do, she says, is “underestimate the sheer force of the executive branch raining down on you.” And what all endure is a cavernous loneliness. “It’s this weird netherworld, very lonely and isolated,” she says. “And when you are charged with the Espionage Act”—as Snowden has been—“you are radioactive. You may as well be charged with being a pedophile cannibal.”

To this day, no one, maybe not even Snowden himself, really knows how many documents he took; estimates vary wildly. Snowden cautions about some of the numbers that investigators have publicized, especially the 1.7 million figure, which, he says, is “simply a scare number based on an intentionally crude metric: everything that I ever digitally interacted with in my career.” He adds, “Look at the language officials use in sworn testimony about these records: ‘could have,’ ‘may have,’ ‘potentially.’ They’re prevaricating. Every single one of those officials knows I don’t have 1.7 million files, but what are they going to say? What senior official is going to go in front of Congress and say, ‘We have no idea what he has, because the N.S.A.’s auditing of systems holding hundreds of millions of Americans’ data is so negligent that any high-school dropout can walk out the door with it’?”

Equally mysterious is who actually has the documents. Snowden is adamant: “I know exactly how many documents I have. Zero.” But for the other players involved, “I’m not sure we’ll ever know who has what,” The Guardian’s Janine Gibson says. Greenwald has said that only he and Poitras possess a full set. David Miranda, Greenwald’s boyfriend, carried some documents, encrypted on USB sticks, through Heathrow, on August 18, on his way home to Rio after a week in Berlin. He was detained by British authorities for almost nine hours—the longest time frame allowed without arrest under the country’s terrorism laws. Miranda’s flight was paid for by The Guardian, but the paper’s editor, Alan Rusbridger, didn’t know who Miranda was until he got a call about the detention, because Greenwald had booked the flight through the New York office.

Shortly thereafter, Rusbridger went public with another of the newspaper’s tangles with the British state. From the beginning, he was obsessed with keeping the 50,000 or so documents Snowden had given MacAskill in Hong Kong safe. To handle them at The Guardian’s offices in London, the paper set up a special room, watched at all times by a security guard with a list of names of people allowed entry. Paper covered the windows, blocking any view, and the computers were “air-gapped,” meaning that they had never been connected to the Internet. Documents were stored on USB sticks and never touched a network. Cell phones weren’t allowed inside, for fear that they could be used to somehow listen to conversations in the room or, worse, suck up the documents from the computers. The journalists didn’t know what the GCHQ or other spy agencies were capable of doing, so they imagined the worst.

On June 16, 2013, The Guardian published a story detailing how British and American intelligence had spied on leaders at G-20 meetings in 2009, hacking delegates’ BlackBerrys and monitoring phone calls. On June 21, as the paper prepared a story on Tempora, a GCHQ surveillance program that collects data by attaching probes to fiber-optic cables, British Cabinet secretary Sir Jeremy Heywood showed up at The Guardian’s offices to tell Rusbridger, “You have had your debate,” and he threatened the paper with legal action. Rusbridger tried to explain the futility of stopping the paper from publishing. The documents, he said, were all over the world, with Glenn Greenwald in Brazil and Laura Poitras in Berlin. Heywood pointed out that the British government was less worried about a blogger in Brazil than a national newspaper. On top of that, he said, the paper was at risk of being spied on by the Chinese or Russians. Plastic cups in Rusbridger’s office could be turned into listening devices. The documents, Heywood suggested, weren’t safe with The Guardian after all. “From my perspective, it was fairly hair-raising,” Rusbridger remembers.

Fearful that the British government would attempt to stop the paper from publishing, Rusbridger handed the documents MacAskill had given him to ProPublica, a nonprofit journalism operation in New York, for safekeeping. Then, seeking further safety for the documents, he called Jill Abramson, executive editor of The New York Times, and asked her if the paper could “store” the documents. He gave her no guarantee they could see them, but Abramson agreed. When Snowden found out about the handover, he was livid, and claimed that The Guardian had broken its agreement with him. He had explicitly avoided The New York Times, due to the paper’s decision to delay publication for nearly a year of its 2005 story detailing the N.S.A.’s Bush-era warrantless wiretapping. (Asked about this episode today, Snowden says, “The final public-interest decisions about journalism should be made by journalists.”) The Guardian continued publishing Snowden-related stories for two more weeks, until July 12, when Heywood dropped by again, this time to propose that the government come in and tell The Guardian how to keep the documents safe and eventually destroy them. He said the agency was worried about the 30 or 40 documents The Guardian had. Six weeks after the initial leak, the authorities still had no idea of the sheer volume of documents the journalists actually had.

Rusbridger agreed to the meeting. But the next week, the prime minister’s press secretary texted with a dire warning that the paper needed to hand over the material immediately … or else. “It was so apparent that we would report it elsewhere and the material existed elsewhere,” Rusbridger recently recalled. “Nevertheless, there was a new steel and determination, and they wanted to stop us.” Rusbridger refused to give up the material, but he agreed to destroy what was in The Guardian’s London office. That afternoon, Abramson and her managing editor, Dean Baquet, went to the office, and Rusbridger gave them a list of 14 conditions for handling the material. The Times had to set up a secure room in its newsroom. According to Rusbridger, both papers could work on stories, but only the Guardian reporters could have access to the raw documents. Abramson agreed to the terms.

That Friday, July 19, two GCHQ men came to the Guardian offices with a machine to erase hard drives. They told the editors that they would have to use various drills and masks to protect against the sparks and smoke. The next day, they came back, and the editors took turns destroying the material that had given them the greatest scoop of their careers. Later, Rusbridger would carry around pieces of the destroyed hard drives, almost as totems.

“Foreign media outlets will publish anything on a foreign government,” Greenwald says. “People are much more conservative when it comes to reporting on their own governments. That’s why it was so stupid of the British government to destroy the Guardian hard drives.”

Silicon Valley’s response to the Snowden leaks was fraught from the beginning. In the early coverage of Prism, companies like Apple, Google, and Yahoo denied knowledge of the program, prompting The Washington Post to update the online version of its story to incorporate the denials. It eventually became clear that these denials were a combination of honest ignorance—very few people inside the companies understood the terms under which they were cooperating with the N.S.A.—and a game of semantics. What it meant to “collect” someone’s information or to have “direct access” to a company server depended on how one defined those terms. Later, when the Post, reporting on an N.S.A. program called Muscular, described how the N.S.A. and GCHQ intercepted information as it flowed from one data center to another, the story was met with multiple seeming denials from Obama-administration officials. It wasn’t until Gellman and his technical adviser, Ashkan Soltani, reported a follow-up story, which described the technology in detail and showed the denials for what they were, that the full weight of the program became apparent. After the second story ran, a Google engineer who had spent 10 years working in the company’s online-security division posted a personal comment about the story: “Fuck these guys,” he wrote, referring to the N.S.A.

The secrets revealed by Snowden to journalists have been vast and wide-reaching. Barton Gellman’s stories alone, in The Washington Post, have not only disclosed the Prism program but also revealed the U.S. government’s secret $52.6 billion “black” budget for intelligence gathering. Gellman showed that the N.S.A. collects hundreds of millions of address books globally and five billion records a day on the whereabouts of cell phones and their users. In addition, he revealed Muscular, which is even more aggressive than Prism in collecting user data. What the U.S. government fears most is not what Snowden has so far disclosed but what he possesses that remains secret. “We still don’t know exactly what documents he took,” says Ledgett. What the N.S.A. does know, he says, is that Snowden made off with at least 36,000 pages of what Ledgett refers to as “the keys to the kingdom.” By that he means “the whole database of requirements,” or orders, from government agencies—the State Department and the Departments of Transportation and Homeland Security—to the N.S.A. requesting specific foreign-surveillance information. That data reveals not only what the United States knows about the military systems and intelligence operations of countries including Russia and China, but also what it doesn’t know. In addition to containing embarrassing revelations about spying on allies, the documents purportedly detail current operations against nations hostile to America’s interests. What the world has already learned may well pale in comparison with what remains under wraps. Intelligence officials whisper about “a doomsday cache” in Snowden’s possession. Snowden retorts, “Who would set up a system that incentivizes others to kill them?”

The Snowden episode is far from over, and it’s hard to imagine exactly how it will end. Glenn Greenwald and Laura Poitras parlayed their documents into a new media organization funded by Pierre Omidyar, the deep-pocketed eBay founder. They promise to continue their reporting on the N.S.A. based on Snowden’s documents. There are several initiatives in Congress, the most prominent of which, the U.S.A. Freedom Act, is an attempt to stop bulk collection of Americans’ phone records and to revise the FISA courts.

In late March the Obama administration announced a legislative proposal to end the N.S.A.’s bulk collection of Americans’ phone records. Under the plan, specific records could be obtained only by using a new kind of court order that involved permission from a judge. Once the requested records were obtained, a judge would also have to rule whether the N.S.A. could gather additional, associated records.

On October 9, Snowden was photographed standing beside Sarah Harrison on a boat on a river somewhere in Russia. They lived in a secret location, though one source close to Snowden says that they moved multiple times and at one point lived with an American family outside Moscow. Snowden and Harrison’s time together “was a little bit of a love-hate thing,” says a person close to WikiLeaks. “They were stuck in close quarters there for a long time.” Snowden is fastidious and Harrison is not, this person says. He griped about having to do all the dishes. Politically, they saw eye to eye on surveillance, but little else. The day after he was photographed with Harrison, Lon Snowden arrived in Moscow for a six-day visit with his son—it was the first time they had seen each other in six months. They met in a secret location, and even Lon wasn’t told where his son was living, he claimed. “I could be comfortable living the rest of my life [in Russia],” Lon later told reporters. “I’m certain that he could.” One of Snowden’s Russian lawyers said at the time that Snowden was soaking up Russian culture and learning the language, even reading Crime and Punishment, but he has since applied for asylum in more than 20 countries, according to CNN. Harrison moved to Berlin in November, but shortly before she did, a German politician had dinner with her and Snowden, who expressed a desire to be granted asylum in Germany or another democratic state. Mostly, the politician says, Snowden wished he could go home.

For an article published in December by The Washington Post, Barton Gellman spent 14 hours interviewing Snowden in Moscow, during which time, Gellman wrote, Snowden never once stepped outside or opened the curtains. He characterized his new life as that of an “indoor cat.” This March 10, in his first public appearance since last July, Snowden addressed thousands of attendees in a live feed at this year’s South by Southwest conference, in Austin, Texas. Though the connection, routed through several proxies to conceal his location, was spotty, Snowden reiterated his call to action: “The key is accountability. We can’t have officials … who can lie to everyone in the country…. We need public advocates…. We need a watchdog that watches Congress.” Focusing on technology and policy and saying nothing about his life in Russia, he urged tech companies to help regain the public trust by using—and improving—encryption and other privacy technologies. “Let’s put it this way: the United States government has assembled a massive investigation team into me personally,” he said. “They still have no idea what documents were provided to the journalists, what they have, what they don’t have. Because encryption works.”

Greenwald, speaking from Brazil to the SXSW crowd via video later that day, confirmed that he had read all of the documents Snowden had given him. “The most shocking and significant stories have yet to be reported,” he said.

As Vladimir Putin pursues an increasingly aggressive anti-Western agenda, Snowden’s asylum in Russia has, in the eyes of some, taken on a sinister, new-Cold War cast. In mid-October, Snowden told The New York Times, “There’s a zero percent chance the Russians or Chinese have received any documents.” But Snowden’s actions have exposed dangers to democracy at least as great. We now know that the so-called “deep state”—a government within a government, organized around secrecy and surveillance—is not just the stuff of conspiracy theorists and writers of thrillers. Surveillance apparatus, however necessary some of it may be, has so far proved impossible to control. Safeguards against widening surveillance will have to come from outside government—frankly, from the ideas and expertise of people like Edward Snowden.

When Snowden boarded that plane in Honolulu last spring, he passed irrevocably into a new life and a new world. And so did we. “What we’re seeing today in America is a new political movement that crosses party lines,” he says. “This post-terror generation rejects the idea that we have to burn down our village in order to save it—that the only way to defend the Constitution is to tear it up.”

Additional reporting by Lenora Jane Estes and Michael Joseph Gross.

note: An earlier version of this story misstated the U.S. government’s charges against Edward Snowden. Federal prosecutors filed a criminal complaint against him. He was not indicted.