The setting is now Boston, the situation one of corruption, infighting within the police and ruthlessness among mobsters, with a touch of old neighborhood ties figuring in the relationships. Matt Damon is convincing as Colin Sullivan, a cop who turns corrupt, serving as an informer for gangster Frank Costello by tipping him off on moves against him. Leonardo DiCaprio turns in a stalwart performer as Sullivan’s counterpart, Billy Costigan, a cop who goes dangerously undercover within Costello’s gang. Each side desperately wants to expose the traitors.

Towering over everyone’s acting impression is that of Jack Nicholson as the ruthless Costello. Nicholson is remembered for many over-the-top acting performances, and he will certainly be remembered for this one, a nasty, although sometimes funny, portrait of a brutal, vicious gang boss. The savvy Nicholson gives extra life and spark to the wicked story, and his participation is a huge entertainment factor. Martin Sheen, Mark Wahlberg. Alec Baldwin, Ray Winstone and Anthony Anderson all do right by their assorted roles.

A major screenwriting problem, apart from twists and turns one usually can question in films of this sort, involves Vera Farmiga as Madolyn, a psychiatrist whose practice includes being a shrink to cops. Sullivan and Madolyn become an item, and so do she and Costigan. Farmiga’s acting is impressive, but her character is demeaned by the unprofessional way in which she is involved, and although there are connective reasons for the entanglement, it doesn’t ring very true.