'Zero Dark Thirty': The Story Behind The Real-Life CIA Agent

Jessica Chastain talks portraying the mind behind the killing of Osama bin Laden.

The usual advantages of portraying an actual living person didn't apply to Jessica Chastain with her role as Maya in "Zero Dark Thirty." The woman responsible for finding Osama bin Laden is an undercover CIA analyst, who wasn't exactly available for interviews or chats over coffee with Chastain as she prepared for the role.

"No, I can't call her up and say, 'Hey, can I go undercover with you to see what it's like?' I don't think you understand undercover," Chastain told MTV News' Josh Horowitz while doing press for the film.

But the serious nature of the film required accuracy on Chastain's part, so she had to turn elsewhere for the truth about Maya. One indispensable resource was former journalist and "Zero Dark Thirty" screenwriter Mark Boal.

"Having Mark Boal — our screenwriter used to be an investigative journalist — was a great help. I had three months before we started shooting to basically go to school," Chastain said. "I nicknamed him 'The Professor,' and I just picked his brain about everything he knew about the CIA, everything he knew about Maya, about the relationships, seniority with other colleagues, and I just started reading books on bin Laden and the war on terror."

Of course, not every detail about the life of the CIA agent was privy to Chastain, who then was left to fill in the blanks herself. "Anything I could not discover from my research, I had to fill in the blank, but fill in the blank and stay true to who the idea that Maya was," she said. "I couldn't fill in the blanks with Jessica Chastain knowledge. 'She went to Julliard before the CIA.' "

Answering those questions in a way that stayed true to the actual person was paramount to Chastain's portrayal of Maya, even if that meant going against her own instincts.

"I think the whole point is that I'm playing a true person and this is exactly what she did. She didn't have a boyfriend. She didn't have the guy at home after she had a hard day, who is like 'Hey, babe. Let me make you dinner.' That didn't exist for Maya," Chastain said. "She, over a decade, kind of went down the rabbit hole, getting lost in her work, until finally at the end of the movie, [the pilot] says 'Where do you want to go?' She has no idea where she goes now. Who is she now? She's trained to be unemotional and analytically precise. I'm trying to be the exact opposite. I'm trained to be emotional and kind of a hot mess, so that was a bit of a stretch."

Check out everything we've got on in "Zero Dark Thirty."