Last night at the 87th Academy Awards, the winner for documentary feature was Laura Poitras’ film Citizenfour. It’s a fascinating film that chronicles the 2013 whistleblowing by a CIA analyst named Edward Snowden, who discovered, and then fled the country in order to disseminate, classified documents that pointed to the NSA’s ability to access personal date from Americans everywhere anytime it wanted to, with near impunity. It’s a very troubling film that’s far more tense and thrilling than even the most bombastic Hollywood spy film, even though it’s mostly just people talking in rooms.

Citizenfour, having been produced by HBO Films, is airing tonight at 9:00pm on HBO, giving millions of subscribers the opportunity to see it. It’s highly worth watching.

Poitras has been a highly political and socially-charged documentarian for a number of years, and following her 2006 Oscar-nominated documentary, My Country, My Country, which chronicles life in Iraq during the U.S. occupation, claims she was placed on the Department of Homeland Security’s watch list. It was this that gave Snowden, under the anonymous name “Citizenfour,” the idea to reach out to her to tell his story as it was happening. He also reached out to former Salon and Guardian columnist Glenn Greenwald, who was the one who published Snowden’s findings and got the whole ball rolling.

Whether you agree with what Snowden did or not, and the film does mainly come down on the side of his actions being just, Citizenfour is a chilling and paranoid film about what the U.S. Government is capable of following 9/11 and the beginning of the Patriot Act. Poitras gets unprecedented access to Snowden at a time when nobody knew who he was and we get to see how careful he feels he has to be, probably with good reason, in order to get the information out without being found out. He’s a man who’s not afraid to share the information, but is very afraid of what might happen to him and his girlfriend should it all get out. There are whole chunks of time where nobody can really be sure if things like a fire alarm test in a Hong Kong hotel are just coincidence or somehow the government types knowing what he’s up to.

If you haven’t yet seen Citizenfour, or even if you have, it showing on HBO is a great excuse to see it now. It’s a hugely important film about what is or is not legal for the government to obtain from the American public, and it’s not a topic that’s simply gone away in the intervening years.