Hard as it might be to believe, the tensest movie of the year is a documentary primarily dedicated to two-to-four people sitting quietly in a hotel room. Like all great documentaries, Laura Poitras’ ‘Citizenfour’ is a product of good fortune and talent. Poitras was lucky enough to be the director contacted by Edward Snowden to film his NSA whistleblowing, and she was talented enough to know to shoot it like a thriller rather than merely sitting back and observing. In the process, she made a contemporary ‘All the Presidents’ Men’, only even more frighteningly real.

Just over a year ago, documentary filmmaker Laura Poitras received instructions for how to read an encrypted email from a mysterious source known as Citizenfour. She was selected because the first two chapters of her 9/11 documentary trilogy (‘My Country, My Country’ and ‘The Oath’) earned her a spot on the NSA’s watch list, ensuring that no border crossing would pass without incredible difficulty. Citizenfour was Edward Snowden. At the time, he was an inconspicuous tech guy working at the NSA, but of course now he’s the most famous whistleblower of the decade hiding out in Russia. Because of the privileged access of his job, Snowden knew just how deep and illegal the NSA’s international digital monitoring could reach. In a selfless act that would ensure he’d spend the rest of his life living in exile, he decided to tell the world. How he did that would be tricky. Knowing that it could cost him his life and that the story could all too easily be washed away with personality attacks, he approached the leak strategically. He picked a journalist that he could trust in Glenn Greenwald and also chose Poitras to document the story as a film just in case things went wrong. The resulting doc that Poitras delivered is as vital a work of American filmmaking as any to arrive in 2014.

In an act of good faith, Poitras and Greenwald flew to Hong Kong to meet their mysterious source. It turned out to be the mild mannered, yet intimidatingly intelligent and calculating Snowden. Their first meeting merely entailed Snowden explaining who he was and revealing the NSA’s terrifyingly long reach in the broadest scope. He admitted that he didn’t want to be the center of the story at first. He wanted only the facts to leak initially so that news organizations would run with that story before his own. So, Greenwald (along with his Guardian colleague Ewen MacAskill) did exactly that.

The story blew up the international media and Snowden’s girlfriend was immediately interrogated by his former bosses without anyone officially knowing whom he was. Then he revealed his identity, and within 24 hours news organizations were flooding his Hong Kong hotel room with calls, prompting him to change rooms before going into hiding. Throughout the ordeal, Poitras kept her cameras soberly pointed at her subjects. They never left his room out of fear of detection, and Snowden goes so far as to log onto his computer under a blanket and unplug his hotel phone in case he was recorded. His behavior may have seemed overly paranoid at first, but as soon as the facts came out, it became clear that his intense security measures might not have been enough.

If you followed the Snowden story last year, there’s not a hell of a lot of new details about the NSA’s tactics revealed in the film that will come as a surprise. In accordance with Snowden’s wishes, all the important details were already made public. However, simply watching him reveal the information and the terrifyingly true security tactics necessary to do so makes for an absolutely riveting watch. Poitras never succumbs to the temptation of over-stylizing her documentary to feel like a thriller, but she’s wise enough to give herself enough material to edit with the rhythms of suspense. Helped in no small part by sweaty-palmed score by David Fincher’s regulars Trent Reznor and Atticus Ross, ‘Citizenfour’ can be an almost unbearably intense movie to behold, even though it’s only about a few people calmly talking in a room. The reason is simple: the horrifying Big Brother-esque government monitoring tactics they discuss are all too real. We know that not just from the documents that Snowden leaked, but also from how dramatically his life changed the moment it happened.

Is Snowden guilty of treason? Well sure, there’ no doubt of that. Yet given how important it is that the information he revealed be made public, the well-being of the global community justified the means. Some might complain that Poitras never really dabbles in the negative implications of what Snowden did, but at the moment, that’s not as important as focusing on the bravery required. There will undoubtedly be many movies made about the issue from a variety of perspectives. This is the only the first, and a first-person account of what happened is the most vital take to see right now. The fact that it even exists is a bit of a miracle and a canny move on Snowden’s part, a man well aware of how the media could be used to manipulate his life to cloud the issue.

By the time the film ends, its maker and subjects know that they can never again live in the United States, and that they’ll have to live the rest of their lives under intense scrutiny and monitoring from the country they abandoned. Yet, they ultimately remain patriots because what they revealed can never be unlearned. Aside from its cultural significance and exquisite use of film language, ‘Citizenfour’ is an impossible movie to shake because of the leaked information at its core and the implications that Poitras leaves dangling to haunt her audience. When you leave the theater and impulsively look at your phone, you can’t help but remember that you’re holding a personalized device that is the most complex piece of surveillance technology ever conceived. We now all own a camera, microphone and tracking device that sends out personal information to the U.S. government daily. And here you just thought it was an ‘Angry Birds’ toy and dating aid.