Whether you think Edward Snowden is a hero or a traitor, you should see the riveting documentary “Citizenfour,” at the very least to get to know better the young man who just a little over a year ago became one of the most pivotal — and shadowy — figures on the geopolitical stage.

In early 2013, Snowden, working as a private security contractor for the National Security Agency, contacted journalist and filmmaker Laura Poitras under the alias “Citizenfour” with information about the reach and extent of NSA’s surveillance of private communications.

A few months later, Poitras and her colleague, investigative reporter Glenn Greenwald, met Snowden in Hong Kong — their initial encounter choreographed with intrigue worthy of John le Carré, complete with code questions and the modern-day equivalent of a red carnation in the lapel. After retiring to Snowden’s hotel room, he proceeded over eight days to share what he knew. Poitras persuaded Snowden to let her film the encounter, and the resulting footage forms the bulk of “Citizenfour,” which unfolds like a real-life thriller, at once mesmerizing and banal, as just another faceless bureaucrat in the national security state transforms, quite literally, into an international man of mystery.

Poitras, whose previous films include “My Country, My Country” and “The Oath” — both of which addressed post-9/11 foreign policy — was prescient in asking Snowden for permission to film: “Citizenfour” isn’t just a useful primer in the civil liberties and consent issues his disclosures raised. It humanizes a man who almost immediately became controversialized as a naive, self-important desk jockey or, worse, a handmaiden to terrorists everywhere.

There’s no doubt that Poitras is firmly on Snowden’s side, but her perspective is still a useful one. What emerges in “Citizenfour” is a serious, thoughtful, deeply idealistic person who — it bears noting — purposefully went to Poitras and Greenwald so that his information would be disseminated according to journalistic standards and practices, not his own bias. As Snowden himself says, it all comes down to a balance of power between the state and its citizens that has become a dynamic of “the rulers and the ruled.”

Not surprisingly, paranoia runs deep in “Citizenfour,” which chronicles how Poitras and Greenwald come under their own forms of government watching (even harassment); the effect is heightened by the claustrophobic room in which they’re trapped for several days, while the story they’re helping create blows up outside.

“Citizenfour” makes a persuasive case that Snowden’s suspicions are justified: Poitras includes damning images of administration officials seeming to lie under oath before Congress, as well as the testimony of mathematician William Binney, who left a 30-year career with the NSA after raising concerns about mismanagement and domestic privacy breaches. As an encryption activist says at one point in “Citizenfour,” invading privacy “is supposed to be hard.”

As sobering as these sequences are, the film is at its most compelling inside that hotel room with Snowden, as he nervously decides when to make his identity known, silently tapping out e-mails to his girlfriend back in Hawaii as an international media storm he started ensues outside. In one of the film’s most evocative passages, Snowden nervously fixes his hair before introducing himself to the world he’s just rocked, puttering around the disheveled room as if tiptoeing through the silent eye of a raging hurricane just outside the walls.

Poitras sets up the last 20 minutes of the film as a series of bombshells that aren’t necessarily as incendiary (or surprising) as she may have hoped. Still, one scene in particular lands with all the drama and intrigue the filmmaker clearly intended: It’s a shot of Snowden, now in Moscow, moving contentedly around his kitchen, an image all the more eerily effective for being taken outside his window, like a spy or maybe a silent, all-observing drone.

★ ★ ★ ½

R. At Landmark’s E Street Cinema. Contains profanity. 114 minutes.