Director: Laura Poitras

Actors: Edward Snowden, Glenn Greenwald

Release Date: Saturday 30th November 2013

Genre(s): Documentary

Running time: Germany minutes

When director Laura Poitras was beginning work on the final chapter of her documentary trilogy dealing with America post-9/11, after 2003's Flag Wars dealing with racism and homophobia and 2010's The Oath which took on Guantanamo Bay, she began to receive encrypted messages from a source that promised to have some very valuable information. Travelling to Hong Kong with The Guardian reporter Glenn Greenwald in tow, they discover that the informant is former NSA employee Edward Snowden, who is ready and willing to blow the whistle on the US government's massive invasion of privacy.

Coming with certifiable proof that the Obama administration has been eavesdropping on phonecalls, emails, texts and Google searches, Citizenfour is a slow burner, but one that becomes so incendiary, it should become something of a call to arms for its viewers. Taking 80 minutes to set up what exactly they've got on their hands and the subsequent consequences of their leaking, it's apparent that in this day and age of technological advancement, it's next to impossible for anyone - even the most powerful government in the world - to keep their secrets.

Of course, that also applies to the whistleblowers, as the final 40 minutes finds Snowden and anyone involved in assisting his leak come under the scrutiny of the international governments they've involved. Jumping from Hong Kong to Berlin to Rio, playing out like a spy novel, along with a very Trent Reznor-y score, this is about as close to a nail-biting political thriller as you could possibly get from a documentary.

This showiness sometimes gets in the way of the film's own story, with Poitras oddly toned narration and complete oversight of Snowden's own backstory; while Citizenfour never takes sides, there is a sense that some important elements have merely been left out of the story for the sake of an easier narration.

Sure to drum up a reaction from audiences, be it for the singling out of Snowden as a political martyr or the mass betrayal by an entire government, all while maintaining a chilling, spine-tingling type of entertainment throughout, Citizenfour is an absolute must-watch.