Committed to inhabiting Snowden’s robotic speech pattern, Gordon-­Levitt lifted the audio from “Citizenfour” and played it on repeat while he slept. He also worried that some of the dialogue felt heavy-­handed. “Oliver is very into making his point,” the actor said, “as he should be. I really admire him for that. But I felt like it was my job to be like, ‘O.K., I want to make the point, too, but this is a human being and not just a mouthpiece.” Stone found Gordon-­Levitt’s approach too “documentary-­ish” at times. “I was trying for the dramatic side as much as possible,” Stone said. Fitzgerald was ultimately flown in to the set to execute last-­minute rewrites.

By late spring of 2015, Stone was close to wrapping when his mother, Jacqueline Goddet Stone, died at 93. She had called him in Munich, but Stone felt he couldn’t risk leaving. “To go to L.A. would have cost us three down days,” Stone told me. “I knew she was going to pass, but I thought I could make it.” Stone remained on set during the funeral and kept shooting.

Stone’s trip to Moscow to film the real Snowden was the last bit he needed to complete the film. But he was still worried — that the footage would be leaked, that critics would eviscerate it, that Snowden wouldn’t like it. “I want him to vet it,” he said. He was heading to New York to begin editing and planned to return to Moscow at the end of the summer to show Snowden a rough cut. “O.K., my dear,” Stone said, getting up to leave. “See you in New York.”

Then he disappeared for six months.

Before Stone set out to make his film, he had met Snowden’s chief biographers, Greenwald and Poitras. Stone and Greenwald became friendly, and when Greenwald’s book drew interest in Hollywood before it was published, the journalist turned to Stone for advice. “In the back of my mind, I thought if he had any interest in making a film, that would be a good segue for him to say so,” Greenwald told me.

At the time, Stone wasn’t interested, and Greenwald negotiated the deal with Sony. Stone later came back and offered to match Sony’s bid, but Greenwald declined. “I think he was a little perturbed,” Greenwald said. Of the principal cast, Zachary Quinto, who plays Greenwald in Stone’s movie, was the only actor who didn’t meet his real-life counterpart as research. “I always thought that was a little weird,” Greenwald said. “I think Oliver thought I had some competitive hostility toward his project, or he had some hostility — I’m not really sure.” (According to Stone, Quinto didn’t need to meet Greenwald because there were so many videos of the journalist online.)

In the spring of 2014, Stone flew to Berlin and met with Poitras. The meeting did not go well. According to Poitras, Stone proposed that she delay the release of “Citizenfour,” which she was then in the middle of editing, to time up with his film. “Because his film would be the real movie — because it’s a Hollywood movie,” Poitras told me. “Obviously I wasn’t interested in doing that. To have another filmmaker ask me to delay the release of my film was — well, it was somewhat insulting.”

Stone was annoyed, but he stuck around for a few drinks. They discussed new movies, including “12 Years a Slave.” As Poitras recalls, Stone found the film too violent, while Poitras thought the brutality was appropriate given the subject matter. Stone was growing increasingly frustrated. “At some point, he reached over and had his hands around my neck,” Poitras said. “It was sort of in a joking way. I think he was a little bit drunk. But it was not a particularly pleasant evening.”