Citizenfour (2014) is a film that seems to unfold in real time. It is as if the plot were revealed to the filmmaker at the same time as the audience. The filmmaker is in the story and while never shown is directly and intimately involved. In the film’s opening sequence, she reads aloud the electronic communications sent to her by her source. The filmmaker is Laura Poitras. The source is Edward Snowden.

From a documentary point of view, Citizenfour is the record of an event that may yet shape the future of our democracies: the 2013 meeting in a hotel room in Hong Kong between Poitras and Snowden. Later they are joined by Guardian journalists Glenn Greenwald and Ewen MacAskill. From that initial meeting over the course of several days and the exchange of information that took place came revelations about tools like xkeyscore and programmes like Prism and Tempora, and about the extent to which a global network of electronic surveillance established and controlled by the United States and its allies reaches into the lives of ordinary people all over the world.

The Hong Kong meeting is at the heart of the film, and will justly command its place as a document of genuine and lasting historical interest. But Citizenfour is also, and I want to suggest more poignantly, the story of multiple exiles. Snowden, who will most likely never set foot in the United States again unless he is a prisoner, is not the only one in exile. It is also about Poitras, who, after years of harassment by border authorities as a result of her work has moved to Berlin, and Greenwald, who discusses with Poitras at one point how it would be imprudent to return to America for the time being.

The United States is to be understood in the film both as the literal place Snowden, Poitras and Greenwald were born, but also as a power that reaches outwards, exercising surveillance, threatening extradition, interfering in your work wherever you may live.

It is a truism to observe that the more the internet has insinuated itself into the fabric of our lives, the more vulnerable we have all become to being spied upon and monitored. Hence the unsurprising mundaneness of crime-thriller scenarios and representational conventions in films like Enemy of the State (1998) or the Bourne Identity (2002) with which most people have become tritely familiar. Yet no other film before Citizenfour – not even Francis Ford Coppola’s classic The Conversation (1974) or Florian Henckel von Donnersmarck’s celebrated The Lives of Others (2006) – had evoked for me the sense of claustrophobia and oppression or the full intimacy of the intrusion in the personal by the surveillance apparatus.

Control is a force that prevents communication by forcing us to self-censor: and so Citizenfour focuses on the difficulties of the exiled in talking to one another. There are long electronic trails prefaced by blocks of encrypted text, sometimes resulting in failure when it cannot be confirmed that it is safe to talk.

The main character, Snowden, is both present and absent. He speaks through Poitras’ voice in the first act, when he is still known only by his handle, ‘Citizenfour’. He occupies the screen for a full hour in the second, confidently at the beginning, then more and more anxiously as the two alternate futures he had anticipated – imminent capture or a protracted, possibly life-long seclusion – draw near him. He disappears again in the third, as Poitras can no longer reach him. Thus, we are unable to be with him during those forty, undoubtedly surreal days he spent at Moscow’s Sheremetyevo Airport. Nor do we witness the circumstances of his settling into a new life and a new kind of normalcy after the granting of his temporary Russian asylum. Here the film loses itself somewhat, suspended between the clinical political essay and the impassioned documentary orphaned of its central character.

When we encounter Snowden again, it’s by means of an extraordinary shot through the kitchen window of his new home. Here we find that he has been joined in Moscow by his long-time partner, Lindsay Mills, whom he had left before travelling to Hong Kong without a word of explanation. This was so he could carry out his plan without implicating her. The two are making dinner.

The camera and the microphone used to be the main tools for electronic surveillance, which has always placed cinema in a somewhat awkward and structurally ironic position with regards to these issues. When we are immersed in the lives of the characters of ordinary narrative films we are not just implicitly cast as voyeurs, but also as omniscient, all-reaching government spies. The silent shot of Snowden and Mills filmed by a camera placed in the darkness outside their Moscow home reproduces this relationship in the era of computer surveillance, when seeing is no longer the principal or most effective way of knowing. The image is no longer essential or even useful. They can tell more about you by your metadata.

Outpaced, outmoded, cinema struggles to express this reality except by resorting to older tropes. Shooting Snowden and Mills as if they were under direct visual monitoring by the agents of a secret police gestures metaphorically at the scenarios described in the film by Snowden. In our surveillance paradigm, new and even more ruthlessly pervasive technologies of intrusion are able to capture, by plugging into your search history along with your communication patterns, not just whom you consort with and the content of your speech but also your desires. If Citizenfour tells this story imperfectly, it’s because we haven’t yet developed an adequate language for it.