In his post-9/11 novel Pattern Recognition, science fiction writer William Gibson combs through the emotional fallout of that disaster to examine what paranoia does to the human mind. The main character's father, a Cold War security expert named Win, disappeared in Lower Manhattan that day. His views on paranoia are scattered through the book like nuggets of wisdom or total insanity -- depending on the reader's paranoia level.

After spending his life securing American embassies against Soviet incursions, Win treated paranoia like a tool, "as though it were something to be domesticated and trained.

"It was there, constantly and intimately, and he relied on it professionally, but he wouldn't allow it to spread, become jungle," Gibson wrote. "He cultivated it on its own special plot, and checked it daily for news it might bring: hunches, lateralisms, frank anomalies.... He was also fond of saying, at other times, that even paranoid schizophrenics have enemies."

Paranoia is having something of a moment in America. A full-on Ebola outbreak is highly unlikely here but fear of the disease has become contagion, made paranoia, in Gibson's terminology, "jungle." A milder, perhaps more reasonable form of paranoia is also on display in what is sure to be the most talked about documentary of the year, Citizenfour, Laura Poitras's portrait of Edward Snowden and the American intelligence system. The film's characters are constantly looking over their shoulders, unplugging phones that the National Security Agency might -- but probably isn't -- using as remote microphones, and talking about encryption and an unspecified kind of danger, always undefined but looming and certainly imminent.

Last week FP spoke with Poitras, who was instrumental in facilitating Snowden's revelations about mass surveillance and whose work focuses on America's reaction to the events of 9/11. When she said that her sources in German intelligence tell her that American surveillance has her "lit up like a Christmas tree," it was hard not to be reminded of Gibson's on-again, off-again relationship with the benefits of paranoia.

Paranoia of another terrorist attack, or attacks, has driven the knee-jerk response to al Qaeda's Sept. 11, 2001, attacks on New York and Washington and the subsequent self-inflicted disasters it provoked in Afghanistan and Iraq. And the extreme actions of the U.S. government -- everything from the invasion of Iraq to the Obama administration's crackdown on whistleblowers -- has prompted the activists fighting back against that security state with no small measure of paranoia.

Poitras says her documentary sprang from her belief that "there's something that's gone wrong in our country" in the aftermath of 9/11. Secrecy, lack of accountability, and runaway executive power have become hallmarks of the U.S. government, she says.

Snowden has altered that balance somewhat, pulling back the curtain on American intelligence gathering. "We have people who are taking risks to do something that actually the government should be doing, which is informing people of their policies," Poitras says. Implicit in that is the need for solidarity with these whistleblowers.

"It's not that he doesn't think that there are some legitimate uses of surveillance," Poitras says of Snowden, on whose behalf, she emphasizes, she is hesitant to speak. "What he feels is not right, what the government should not be doing, is this kind of bulk, dragnet, suspicionless collection where you just ingest as much as you can."

The heart of Poitras's film plays out in Hong Kong hotel rooms in interactions between the whistleblower and the journalists who have come to speak with him. The result is something the public rarely sees: earth-shattering journalism as it happens and before it goes viral. For those who have followed the Snowden story, that footage is surreal. It's almost like opening an engine in operation, but more melancholy and anxious. Snowden sits, disheveled, on a hotel bed as he spells his name for a Guardian reporter.

"A person, a source, had crossed the point of no return in their life," Poitras says. "To me that elevates things to a much more interesting level of questions about human nature, and risk, and why, and motivation." Poitras calls the Hong Kong meetings "a rare moment of journalistic encounter that probably I will never witness again."

But Poitras has a complicated relationship with Snowden, who serves both as her source for countless prize-winning articles and also as a documentary subject. Many critics have seized on that relationship, including myself, to argue that she is perhaps too close to Snowden and that she tries to protect him in the film.

That criticism partially stems from how hidden Snowden's personal life remains to the audience, including his relationship with the girlfriend he leaves behind in New York. That was buttressed by George Packer's claim in the New Yorker that Poitras had turned down an opportunity to interview the girlfriend, Laura Mills, but Poitras says that isn't true. Mills, Poitras says, wasn't ready to go on camera.

(Even if she had been, Poitras isn't sure she would have made it into the film. Instead, she's briefly featured in a long shot that feels almost like a piece of surveillance footage cooking dinner with Snowden somewhere in Moscow.)

Poitras believes that the personal consequences of Snowden's decision -- both for himself and Mills -- are evident in the movie and her method for rendering Snowden's inner life is a useful way to understand Poitras's filmmaking technique. In the movie, Snowden is seen instant messaging with Mills on a computer. The audience doesn't see the content of the messages but learns from Snowden that Mills has received a visit from the police. Snowden looks dismayed as he delivers the news.

Prying eyes -- including those of this writer -- were left wanting more, but Poitras has a good response to her critics: "I like the fact that the audience has to read in." Indeed, by that measure the documentary is a success. I left the theater feeling somewhat anguished about whether I could ever give up the entirety of my material life for a cause I believe in wholeheartedly.

Could I leave my life, my possessions, and my girlfriend behind to poke a finger in Uncle Sam's eye? Probably not, I have since concluded.

Citizenfour, which is already playing in a handful of theatres, will open to a wider audience tomorrow.

Stephen Lovekin/Getty Images for HBO