'Zero Dark Thirty': Bin Laden Manhunt Film Based on Controversial Firsthand Accounts: 'Nightline' Exclusive

Kathryn Bigelow's new film had an alternate 'mission failed' ending.

Nov. 26, 2012— -- It was the greatest manhunt of all time, the stealthy nighttime raid by the elite SEAL Team Six on Osama bin Laden's compound in Pakistan, which led to the death of the world's most wanted terrorist leader.

It is the subject of "Zero Dark Thirty," a riveting new film by director Kathryn Bigelow and screenwriter Mark Boal, both of Oscar-winning "The Hurt Locker" fame. But when they began making a film about the hunt for bin Laden six years ago, right after they finished "The Hurt Locker," the movie they had in mind was about the failed attempt to find bin Laden in the Tora Bora mountains of Afghanistan.

That plan changed drastically on May 1, 2011 when bin Laden was killed. Boal, a meticulous investigative reporter, picked up the phone and started working his sources.

"It was a thrilling journey to go on and also thrilling to discover what the people who were involved in this mission were really like," Boal said.

In an exclusive interview with "Nightline," Bigelow and Boal talked about bringing "Zero Dark Thirty" to the screen based on Boal's interviews and Bigelow's dramatic vision. Raddatz first met the filmmaking duo while Bigelow and Boal worked on "The Hurt Locker" and had shared her insights with them about Afghanistan, where she has frequently reported.

"It was all based on first hands accounts so it really felt very vivid and very vital and very, very immediate and visceral of course which is very exciting as a film maker," Bigelow said.

Bigelow said she and Boal were working in his office when they heard President Obama's now famous announcement that the United States had "conducted an operation that killed Osama bin Laden."

"It was a personal moment for me because I grew up in New York City," Boal said. "I think for a lot of people, just kind of an overwhelming moment."

All of a sudden, Bigelow said it put their project in a very different perspective.

"It was not just as a film concern, it was kind of a global concern," she said. "We both realized simultaneously that we had to pivot."

"I picked up the phone and started calling sources and asking them what they knew and taking referrals and knocking on doors and really approached it as comprehensively as I could," Boal said.

Almost immediately, the filmmakers found themselves in the middle of an election year firestorm, accused of receiving classified documents to bolster the president's role. It's something they both deny.

"I certainly did a lot of homework, but I never asked for classified material," Boal said. "To my knowledge I never received any."

In fact, President Obama makes only a fleeting appearance in the film. The star of this real-life drama is, surprisingly, a young female CIA officer, played by Jessica Chastain, who helps find bin Laden through a long-forgotten courier.

"It was a couple of months into the research when I heard about a woman, part of the team, and she has played a big role and she had gone to Jalalabad and been deployed with the SEALs on the night of the raid," Boal said.

"When I realized at the heart of this hunt, at the heart of this 10-year odyssey was this woman, this young woman who had a kind of tenacity and a dedication and a courage, she would never say no, I was excited to take it on," Bigelow said.

The Story Behind "Zero Dark Thirty"

Both Bigelow and Boal felt a responsibility to accurately portray the lives of the people who normally work in the shadows, their efforts rarely known to the outside world. While some of the dialog is word for word real, based on interviews with the young CIA officer and others, some of the dialog is dramatized and the decade-long narrative of events condensed.

"They were proud of what they had done, but they had more or less resigned themselves to the fact that what they had done is not something they could talk about publically," Boal said. "But one of the things a movie allows people to do is talk in a way that is a little bit freer because they know that movies can change the way people look, [and] that I don't have quite the same standards of having to reveal sources as I would if I was, let's say, running a front page piece in the New York Times."

The climax of the film is, of course, the raid that killed bin Laden. The scene was a challenge for the filmmakers who were presenting it to a world that knew how it ended.

"But they don't know how it happened," Bigelow said. "They don't know, OK what was the choreography of the assault itself, where did they land, where did they crash, who did they kill first?"

Although it only takes up about one-fifth of "Zero Dark Thirty" -- the title comes from the code for SEAL team's landing time of 12:30 a.m. -- the filmmakers said the assault on bin Laden's compound, like the rest of the film, is as accurate as possible. A full scale version of the compound -- no Hollywood facades for this movie – was built in Jordan, where they shot for almost four weeks. The floor, the tile, the carpet, the furniture and the marks on the walls, were copied from images seen in ABC News footage that Bigelow said they reviewed frame by frame.

And the famous stealth helicopters that swept over the border into Pakistan were real Black Hawks with computer generated graphics replicating the stealthy skin. Bigelow said the actors told of the terrifying and challenging conditions their real-life counterparts faced.

"You are in the elements, you are in the wind, you are in the sand, the sound of the rotor wash and you can't see anything. So you imagine what it would be like to land in this place," she said.

And Bigelow takes viewers beyond the clinical news accounts, the soundless descriptions and even though you might think you know how it ends, there is more to the story.

"For both of us I think it's fair to say the story itself and the making of it was really hard but really thrilling and exciting," Boal said. "Because you are at the center of something that is so epic and that doesn't come along very often and I think we were both aware of the fact that we probably won't have another story like this."

"I can't imagine," Bigelow said. "I think it's the story of a lifetime."