08/17/2011 12:04 pm ET | Updated Oct 17, 2011

'The Debt': Unspoken Drama Creates Thrills For Jessica Chastain, Sam Worthington

It is counter-intuitive, at this point in modern cinema, for perhaps the most tension-filled moment in an action-packed thriller to come during the spoon feeding of an elderly man.

Factor in, though, that the recipient of the food was once a mad Nazi doctor responsible for the torture and death of countless Jews, and the server is a young Holocaust survivor, and all of a sudden, the discomfort makes total sense.

"The Debt," the upcoming film starring Jessica Chastain, Sam Worthington and Marton Csokas, features the story of three young Israeli Mossad agents sent to capture and take back for trial the maniacal Surgeon of Birkenau, a Josef Mengele-like figure living and working under a pseudonym in East Berlin.

"I think what's particularly appealing about it is, it's an opportunity to make a really strong, very kind of immersive thriller," the film's director, John Madden, told The Huffington Post, "but one that has an emotional and psychological or moral complexity to it that's completely intertwined with the plot."

The pressure on the agents is immense, coming from directions both political and personal. Charged with delivering some sort of small justice for a devastated people, they embark on a risky adventure that rips open the scabs over their own deep losses in the Holocaust, the pain, haunted memories and anger manifest in their subtle glances, clenched jaws and shaking hands. It is not so much a military mission as a journey through an inner gauntlet, with closeups and shots held an extra beat telling as much of a story as the dialogue and considerable action.

In large part, the stars were able to communicate such emotional wrenching turmoil because they worked to experience it for themselves as best they could all these years later. In seeking to understand her character, Rachel, Chastain internalized her research to create a backstory to inform Rachel's pain.

"There was something I read in this book where this girl, [talks about] this thing she witnessed with her parents during the Holocaust," Chastain told HuffPost. "It was a very descriptive memory, it was incredibly emotional, and I read it and I was so moved by it and I said, okay, this makes sense for Rachel."

Backstory established -- with help from Helen Mirren, who stars in the film as the older, scarred Rachel -- Chastain internalized the pain, spending a miserable Christmas as she continued to research the role and the larger story of the Holocaust. That led to what felt like real life experiences, caught on film. Including her scenes spoon feeding and shaving the beard of the doctor.

"When he's talking most of the time I'm thinking, Don't talk to him, don't listen to him, just feed him," Chastain explained. "Like when I'm shaving him and he says 'You Jews don't know how to kill, you only know how to die,' that was... [I'm thinking], I'm not listening I'm not listening I'm not listening, but at the same time... Rachel also wanted to be like 'You know what? I'm not afraid of you.'"

Rachel has most of the intimate moments with the doctor, as she is charged with actually capturing him in the examination room of his gynecological office. That means posing as a patient -- and going through multiple treatments before he can be positively identified and abducted. The false pretense brings the closest of physical contact, which has its own repercussions once the medical veneer is ripped down.

"He says something that strikes an emotional cord in her about her mother," Chastain remembers, "that's almost humiliating to her because it reminds her of being in the doctors' office, being invaded by this man, and him actually knowing her. It's humiliating to think, this monster knows me."

While Chastain communicated her fear and nerves through trembles and panicked eyes, Worthington's stoicism did the emoting for him, a sort of subliminal message sent from an outwardly powerful presence.

Before he set box office records in "Avatar," Madden had seen Worthington in an Australian film called "Somersault," where he noted that he actor had, "A kind of hidden, emotional, hidden kind of quality where there's a sort of emotional shyness, I suppose, and a kind of vulnerability, which is not something you have to generate but it's just there and it needs to be uncovered."

The part, that of David, an agent who watched his entire family perish in the war, called for a determined stoicism that Madden was so convinced that Worthington could bring, he flew to Albuquerque to visit him on the set of another film and offer him the role.

"I thought that any man that is willing to do that, I'm willing to sign on the dotted line," Worthington told HuffPo. "When you meet him, he's extremely sensitive, very eloquent, he knew exactly what he wanted me to do with the character and told me and I said, 'Alright, I'll do it.'"

As it turned out, doing "it" meant doing very little.

"I was just saying trust that you don't need to do very much, because he's a man that can't articulate his feelings in the story," Madden revealed of his instructions to Worthington. "He's a man who's carrying a colossal burden around with him and is damaged and has sublimated all of that into a kind of purposefulness having to do with the mission he's given himself and the job he's taken."

Worthington took that to heart, putting a determined glare in his eyes and clench in his jawline. Next to their charismatic leader Stefan (Coskas) and Chastain's worried Rachel, he is the focused rock -- at least at first, before a number of plot twists take the mission on a number of unexpected adventures.

As he saw it, the stoicism was the affectation borne of his burden. "Once he succeeds in his mission, the demons and the guilt he might feel about the legacy for his family.. he's buried his family, he's buried all of his demons, he's buried his feelings of hatred," Worthington explained in discussing the psyche of his character. "But because the plan unravels, all of those feelings and demons come out of him."

That the film, in many ways, ends up focusing on these raw emotions owes in part to its subject matter, of course, but it was also a conscious choice Madden made as he made the film.

"The experience of doing it is the experience of doing all the things you'd normally associate with that particular 'ghetto' that drama has become in modern movie making," the director said, "which is about character and choice and guilt and choosing, all of these kind of things that you don't normally associate with the thriller."

The focus on the interpersonal aspect of the story was so singular, in fact, that the dual-track outcome surprised even its stars.

"I didn't really know this movie was a thriller until I saw it," Chastain admitted. "I thought I was making a drama, and then when I saw the first screening of it my heart was beating so fast, I was so tense because it is so thrilling."

"The Debt" hits theaters August 31st.