Critics say Chastain pulls it off seamlessly as "Maya," based on a real-life CIA agent who played a major role in tracking down bin Laden at his hideout in Pakistan.

As the film opens in limited U.S. release on Wednesday, Chastain, who is tipped as a likely best actress Oscar nominee for the role, talked to Reuters about playing a character she could not meet and why the film is an important look at America's role in a dark war.

Q. What did you think when you saw this film finished?

A. "It is a tough one for me to watch, because there is so much responsibility with playing this woman. I find her to be incredible. And I didn't want to change her story or make her a Hollywood version, with a lot of makeup. I didn't want to trivialize what she did ... I want her to like it, but I don't know if she will ever see it."

Q. How did you play someone you had never met?

A. "There was three months of working with (screenplay writer) Mark Boal, doing research, reading lists and talking to people. And then anything I could not solve through research, like what is her favorite candy - 'cause when we are all overseas we have something we do when we are homesick - I had to answer that question myself."

Q. Boal hasn't gone into too much detail about her?

A. "We have to protect her because she is an undercover CIA operative, still working."

Q. What else did you know about her?

A. "When we finished the movie, when the Navy Seal book 'No Easy Day' came out. I raced to go read it, because I was like, 'I need to know if my character is in the book!' And they talk about Jen, the young CIA girl. Well, everything matched up. She was the only one that said 100 percent 'he is there.'... They talked about how she had been on it close to a decade and they were only on it for 40 minutes. They said she was crying on the airplane afterwards."

Q. During filming, were you ever worried about your safety, that the film might be misconstrued?

A. "As an actor you always worry about that. Because you think, maybe someone will see a film and they won't understand the difference between acting and reality. The good thing is, what (director Kathryn Bigelow) and Mark have done, is that they have not made a propaganda film. They tried to make it as authentic as possible and respectful of the actual historical event as they could. That includes showing the intense interrogation techniques that were used. The end of the film - it's not a lot of fist pumping and saying, 'Here is our journey over 10 years and it was so difficult and we finally did it.' It ends actually on a very different note."

Q. Can you elaborate on that?

A. "Well, for me the whole thing is about the arc of this woman. She shows up in the beginning and she is wearing her best suit. She thinks she knows what she is in for, and she is completely out of her element. But over the 10 years, this woman, who has been trained to be unemotional and analytically precise ... we see her struggling to keep it contained for 10 years and as she descends down the rabbit hole of the world she is in.

"So finally at the end when she is asked, 'Where do you want to go?' there is no way to answer that question. ... She has no idea where she belongs, now that this is done. But not only does it speak in terms of that, but the movie ends with that question - where do you want to go? Where do we go now as a country? Where do we go as a society? It is not a movie that ends with an answer, and I find that powerful."

Q. How did you cope with filming the torture scenes?

A. "We filmed in a real Jordanian prison, in the middle of nowhere. The environment wasn't great, especially as a woman.

"They had a lot of trust between the actors, nothing was dangerous or unsafe. There was a lot of discussion to make sure that we weren't doing something that was going to be salacious. They just wanted it to be accurate.

"I know I am playing a character who has trained to be unemotional. But I have spent my entire life allowing myself to be emotional, and allowing myself to feel everything. ... There was actually one day that we were doing a scene, and I said, 'I am sorry' and I just had to walk away, and I just started crying ... it was a very intense experience."

Q. You are a top chance for Oscar nomination. Would that be more or less rewarding for this role?

A. "Because she is still an active member of the CIA and undercover, she can't take credit for what she's done. ... And by making this film, it is my idea as a way of thanking her. It would be very emotional because of that."

Q. You compare your character to getting lost down a CIA rabbit hole. What about your own dizzying rise as an actress?

A. "That's a good question. I do think that next year I need to go somewhere for a month and be in a room by myself and be like, 'Ok, what now Jessica?' But I am nowhere near where she was at the end of this mission."

(Reporting By Christine Kearney, editing by Jill Serjeant and Doina Chiacu)

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