To take down South Boston's Irish Mafia, the police send in one of their own to infiltrate the underworld, not realizing the syndicate has done likewise. While an undercover cop curries favor with the mob kingpin, a career criminal rises through the police ranks. But both sides soon discover there's a mole among them.
Leonardo DiCaprio
as Billy
Matt Damon
as Colin
Jack Nicholson
as Costello
Mark Wahlberg
as Dignam
Martin Sheen
as Queenan
Ray Winstone
as Mr. French
Vera Farmiga
as Madolyn
Anthony Anderson
as Brown
Alec Baldwin
as Ellerby
Kevin Corrigan
as Cousin Sean
James Badge Dale
as Barrigan
David O'Hara
as Fitzy
