Laura Poitras seems to have an instinct for a good story. In an interview on “Uprising” about her new film “Citizenfour,” she told me, “When I first started receiving these anonymous emails [from Edward Snowden], my gut instinct pretty early on was that this was probably legitimate. And then my second feeling was that it’s quite dangerous.”

Still, that did not deter her, nor her Brazil-based colleague Glenn Greenwald, from flying to Hong Kong in June 2013 to meet with Snowden in what would prove to yield one of the most explosive exposés in years, revealing the intrusive mass surveillance of Americans and of huge swaths of the world’s population and their heads of state by the U.S. National Security Agency.

Poitras has a unique ability to tell large stories through intimate portraits of individual people. In 2006, she created a moving portrayal of the U.S. war in Iraq via the eyes of a man named Dr. Riyadh in her film “My Country, My Country,” nominated for an Academy Award for best documentary.

Four years later in her next film, “The Oath,” she explored complex themes of conflicting allegiances that have defined the broader “war on terror” in countries such as Yemen, where men like the subject of her film, Abu Jandal, struggle between pledges to their governments and to al-Qaida.

Now, another four years have passed, and her latest cinematic offering explores a third war, largely invisible until this past year. Even before Snowden reached out to her, Poitras had started filming what would become “Citizenfour,” drawn to Greenwald’s work and his unconventional journalistic style. “I really wanted to see how the ‘war on terror’ has played out here, with surveillance being one of the immediate repercussions after 9/11,” she said. In fact, as she explored the politics of the post-9/11 world, she found herself being targeted as so many others have, singled out for extra scrutiny every time she crossed the U.S. border.

Those experiences led her to conclude that she must have landed on one of the government’s watch lists. “What is disturbing about [being on one of these lists,] Poitras said, “is that there is no due process. You’re put on this list and you’re never told why and you’re never asked a question and it comes with these consequences,” which in her case meant that for six years she was “detained and searched and interrogated” each time she left or returned to the U.S. Despite filing several Freedom of Information Act requests, Poitras has not received any information about why she is on a watch list, whether she is indeed on a list, or even that such a list exists. Ultimately, Poitras found that being on a watch list was “this sort of Kafkaesque maze that somehow I got pulled into, and it informed this film in many ways.” (In recent months, documents obtained by The Intercept, of which Poitras is a co-founding editor, revealed for the first time the criteria that are used to designate people on a watch list.)

Soon she began taking practical steps to protect her work, learning about encryption and other tools that provide some measure of protection against surveillance. Those skills prepared her well for initial contact from Snowden and her subsequent interactions with him.

With no guarantee that she could protect her sources and prevent her footage from being copied or confiscated, Poitras took the drastic step of moving to Germany. In fact that is one of the salient aspects about the story of NSA surveillance: It took an American whistle-blower fleeing to Hong Kong to meet with an American journalist based in Brazil and an American filmmaker living in Germany in order to tell the story of the U.S. government’s mass intrusions into the lives of countless ordinary people.

“It was shocking,” Poitras said about the extent of government surveillance that Snowden’s trove of documents revealed. “The most shocking thing was the dragnet, suspicion-less, ‘collect-everything’ mentality ... that they want to take in as much as they can and hold it for as long as they can. It was shocking to see it in writing.”

As a journalist myself I have naturally followed, as best as I could, the intricacies of the countless revelations since June 2013 published by Greenwald and Poitras, along with their colleagues Ewen MacAskill, Barton Gellman and others. Still, watching “Citizenfour” gave me an eerie sense that I was personally witnessing and experiencing the shock that Snowden’s documents inspired in his initial confidantes.

Poitras and Greenwald were at first surprised at how young Snowden was, so much so that she described it as “disorienting.” She explained, “When we arrived in Hong Kong, we expected to meet somebody much older.” Once they got to know him and his motivations, “then it actually made sense,” she said, because “he’s somebody who grew up very much of the Internet and believed in the Internet’s human potential for communication and to empower people.” After a few years working as a contractor for Booz Allen Hamilton, that myth was shattered, leading him to make a decision to risk his life and freedom to get the word out about government surveillance.

Poitras herself never appears in view of the camera, except through a reflection in a mirror, although her voice quietly and ominously narrates online chats among herself, Snowden and Greenwald. Poitras’ lens in the hotel room in Hong Kong where the earliest meetings between the whistle-blower and journalists took place was so unobtrusive that the resulting scenes ironically appeared as though they were selected from surveillance footage. It wordlessly captured the shock of the journalists, the youthful sincerity of the whistle-blower, and the unfolding tension that mounted as the stories started to get published and Snowden revealed himself as the source to the entire world.

In order to keep the story as true to real life as possible, Poitras made the decision early on to preserve the chronology of her footage and reveal one day at a time how events progressed. During the final stages of completing “Citizenfour,” she and her editor flew to Moscow to screen it for Snowden and his girlfriend, Lindsay Mills, who has moved there to be with him. Poitras revealed that “it was intense to be in the room, because Lindsay for the first time saw what happened and how it unfolded.”

Poitras described to me her cinéma vérité style of filmmaking as “trying to be in the moment, in a place where things are happening in real time, and to try to understand those moments.” But the chance to film Snowden was a “unique and extraordinary opportunity,” she said, because “to be able to document this journalism as it was happening was sort of unprecedented in terms of the reverberations it would have.”

It is a testament to our unique digital age that not only has the government found it easy to sweep up as much information as possible, but that people have found swift ways to undermine that power through whistle-blowing actions such as Snowden’s and through rapid-fire journalism based on those revelations by Greenwald and his colleagues. Poitras’ film was finished and released barely 17 months after the initial meeting with Snowden, but it doesn’t appear at all rushed. The film is visually so sophisticated and packs such a powerful punch that I had to remind myself several times while watching it that it was a work of nonfiction. Indeed, we can only wish that the surreal story of U.S. government surveillance were a work of fiction.

“Citizenfour” opens in theaters across the U.S. on Friday.