Known for her sweet role in the popular vampire franchise, Kristen Stewart toughens up in her new role as a guard who goes to Guantanamo Bay in "Camp X-Ray."

"Make no mistake about it, this is a warzone," the first trailer for the film opens with.

Armed head to toe in Army fatigues, Stewart plays Amy Cole, a new solider assigned to go to the Cuban detention camp. Upon arrival, Cole is warned, "Do not to let them get inside her head." But one detainee catches her attention, as the drama follows her personal connection to the character played by Peyman Moaadi.

Cole becomes personally attached to find justice after meeting the detainee Ali, who says he is innocent after being arrested eight years after the Sept.11 attacks.

J.J. Soria and John Carroll Lynch also co-star in the drama.

Stewart, who has notoriously played the love interest in the "Twilight" series, steals the screen in her role as a conflicted Guantanamo Bay solider. "Never at any point have I sat down and plotted how I should proceed from here on. As soon as you start thinking about your career as a trajectory-like, as if you're going to miss out on some wave or momentum-then you're never doing anything for yourself anyway," Steward said.

Directed by Peter Sattler, "Camp X-Ray" received praise at the 2014 Sundance film festival. Critic David Rooney in a review writes that it was "a powerfully internalized performance from Kristen Stewart, delivering perhaps her best screen work to date."

"This is a minimalist role, a very internal performance ... Everything was living and dying on her face-it was a game of inches, not yards," Sattler says of selecting Stewart for the role.

"Camp X-Ray" opens Oct. 17.