Jack Nicholson stars as Frank Costello, the ruthless boss of an underground criminal empire in Southy, the working class neighborhood on the south side of Boston. Law enforcement agencies have been trying to infiltrate the operation and get evidence that will bring down the mobster.

Southy-born Mark Wahlberg plays the detective running the Massachusetts State Police undercover operation.

"What they did shoot in Boston was cool because we were right near my neighborhood. That was pretty weird, shooting the movie right in the neighborhood where I grew up," he says.

Matt Damon in scene from The Departed

Another Boston-area native, Matt Damon, plays Colin Sullivan: a protege to crime boss Costello who hides his past and enlists in the State Police so he can secretly keep his boss one step ahead of the law.

 "It's really rare in a film of this budget to have characters that are this interesting. Generally, the bigger the budget, the less interesting the characters become and all of us actually had real things to play," he says.

Matt Damon and Leonardo DiCaprio in scene from The Departed

Leonard DiCaprio is Billy Costigan, the undercover State Police officer who gets close to Nicholson's crime boss and whose life is in jeopardy if the informer - Damon's character - discovers his identity.

"These characters are two sides of the same coin in a lot of ways. They come from different backgrounds, but they could have easily made choices the other character made, depending on the circumstances," he says.

"As far as Jack (Nicholson) is concerned, we kind of

Jack Nicholson in scene from The Departed

expected the unexpected," adds DiCaprio. "For me, there were number of different scenes where I had no idea what was going to happen. I think we all knew that if he came on board he would have to grab the reins with this character and let him be free form ...and we all were completely ready for that every day that we walked on set."

Martin Scorsese

"In a way it's a world where the morality no longer exists and I think Costello knows that," says Director and producer Martin Scorsese. "The Departed, though set in Boston and based on a story from Hong Kong, nevertheless mirrors some of his own experiences growing up on the mean streets of New York City. I was very affected by it ...more than the physical violence, the emotional violence around me and it is part of what I am and who I am. Somehow it channels itself into the films, but I see it sometimes as absurd. In this film, I think there is absurdity in some of the violence, but that's just the absurdity of being alive."

"A lot of my work on the film is intuitive, but I did understand the corruption of power in Jack Nicholson's character. (He is) beyond God. He has all the money, he has all the drugs and everything and yet he is still not satisfied and he ultimately sets himself up to be taken in by his sons," adds the director.

The Departed also features Vera Farmiga as a psychologist attracted to both undercover cop DiCaprio and informer Damon; and screen veterans Martin Sheen and Alec Baldwin play rival police commanders. The screenplay, adapted from Infernal Affairs, is by William Monahan.