The centrepiece of Laura Poitras' documentary on Edward Snowden and the extent of the NSA's spying powers that he revealed was collected in the few days of interviews she and Guardian columnist Glenn Greenwald conducted with Snowden while he was holed up in a Hong Kong hotel room.

During the discussions Snowden comes across as very intelligent and eloquent, seemingly quite prepared for a life on the run and the manhunt that would come down on his head. As the film quite rightly prompts (if not asking outright), where is the citizen manhunt for the politicians and bureaucrats that gave the government such invasive powers?

If nothing else, Citizenfour is another example of shooting the messenger who merely provides evidence about how rotten the whole system is even though anyone with any brains knows it (I was reading about ECHELON and similar systems in fringe conspiracy magazines 10 or more years ago).

At first it seems Snowden has an inflated sense of self - sending encrypted message to Poitras (recreated through onscreen graphics), keeping his identity secret and organising clandestine meetings with code words makes it look like he just wanted to play spies.

But when the trio start meeting and talking in Hong Kong he's at pains to make the story about the extent of government spying, not to discuss his own story. As he explains to Poitras, Greenwald, and Guardian political correspondent Ewen MacAskill, he's giving the story to documentarians and journalists to make sure none of his own biases make it into the conversation.

It also becomes clear that he has a level head about what fate will befall him. The film explains how he left his girlfriend without explanation so as not to endanger her, but you can still see the strain on his face when he reports that they've taken and questioned her (probably without much of a soft touch).

It's those elements – where you can see the man cracking under the weight of what he's done – that humanises the story, and whatever Poitras' political leanings (she now lives in Berlin because of continued suspicion and cross examination every time she crosses a US border) they're the moments you're sure she was hoping for the most as a filmmaker.

It's also set against a slow, thrumming horror/thriller musical track that makes it feel like SWAT teams are gathering at the hotel door, ready to waterboard Snowden and throw him in a Guantanamo Bay cell.

It makes you wonder what Snowden thought of the final result. He didn't want it to be about him, but any storyteller in any medium (including Poitras, no doubt) will tell you the most effective method is to tell a story through the people involved.

It's an interesting method because there's little doubt some very expensive Washington PR think tank has been working overtime ever since Snowden's work came to light to make the conversation all about him rather than what he revealed, making him this generation's Salman Rushdie.

It's also a good examination about the lost art of journalism – finding and working a contact who can reveal the truth about what people in power don't want you to know.