Actor Sam Worthington takes on 'The Debt'

Sam Worthington plays a Mossad agent on the hunt for a Nazi war criminal in “The Debt.”

PHILADELPHIA -- With as much humility as he can muster, Sam Worthington wants to correct the notion that James Cameron's "Avatar" is one of the biggest hits in Hollywood history.

"It's the biggest," he says, answering a question about how it feels to be the star of one of the most successful -- no, make that the most successful film in the annals of moviedom.

"You can't really fathom it," he says. "It was a changing point in my life, that's for sure. Not only getting the job and working with Jim, but everything that surrounded it. 'Avatar' turned into an anomaly, basically. ... When you look at the box-office figures and then try to turn those figures into how many people actually saw that film, it's beyond comprehension."

It's safe to say -- and no slight intended -- that "The Debt" will not be the biggest hit in Hollywood history. A taut thriller about a trio of Israeli Mossad agents on the hunt for a Nazi war criminal, "The Debt" is also a love story and an opportunity for six actors to share three roles. Worthington, Jessica Chastain ("The Tree of Life") and Marton Csokas ("The Tree" with Charlotte Gainsbourg) are the young Israeli agents dispatched to East Berlin in the mid-1960s to capture the "Surgeon of Birkenau," living incognito and working as an obstetrician. Ciaran Hinds plays Worthington's character, David, 30 years later. Helen Mirren is the older version of Chastain, and Tom Wilkinson has the part played by Csokas.

Directed by John Madden, "The Debt" toggles back and forth from one story, and time, to the

other, revealing the dark secrets these characters share. And before things turn bad back there in 1966 East Germany, the three dedicated young spies played by Worthington, Chastain and Csokas could be doing "Jules and Jim" -- "Jules and Jim" with micro-cameras, codes and guns.

"That's the thing, the triangle is great," says the Australian actor. "You get the extrovert, the introvert -- my character -- and the woman they're competing for. That, to me, is what the movie is about. These three people each have their own demons that they want to lay to rest, and they think this mission will help them achieve some satisfaction. Of course, it doesn't, and then we see the ripple effect that it has 30 years later."

"The Debt," shot in Bucharest, Tel Aviv, and London, was adapted from a 2007 Israeli film. Matthew Vaughn ("X-Men: First Class") wrote the original adaptation and was, at one point, set to direct. Then Madden ("Proof," "Shakespeare in Love") came along and came to New Mexico to recruit Worthington personally.

"He flew to Albuquerque when I was doing 'Terminator Salvation' there," says the Australian. "I thought, 'Any guy that flies to Albuquerque is a man I'll work with.' "

Worthington, 35, says that both Chastain and Csokas spent considerable time with their counterparts, Mirren and Wilkinson, to establish a continuity and a bond in the roles. He and Hinds, however, met for no more than 45 minutes over the course of the shoot.

"Our processes are a lot different," he explains. "I just said, 'Look, here's how I see the character, here's where his moment of change is, and here's what I'm aiming for. I don't know what you want to do with it 30 years later, mate, to be honest. That's up to you.' "

It is Worthington's -- and Hinds' -- character who has the hardest time coming to grips with the events of the original mission. David is plagued with guilt, with regret.

"I'm the idealist, and he's the aftermath, the broken man," Worthington says of Hinds' incarnation of the role. "It's turned him into a ghost, a shell, after 30 years of trying to rectify it. And Ciaran's got that haunted quality. ... He nailed it on the head."

Worthington and his other "Debt" co-star, Chastain, have a second feature together coming this fall, "Texas Killing Fields," a serial murder mystery. He plays a small-town cop obsessed with the killings; she's his ex-wife.

"We're a divorced couple, with problems in the relationship," he says. "We've already done the courting (in "The Debt")."