Leonado DeCaprio, Matt Damon, Jack Nicholson and Mark Wahlberg
Rookie cop Billy Costigan gew up in crime. That makes him the perfect mole, the man in the inside of the mob run by boss Frank Costello. It's his nob to win Costello's trust and help his detective handlers bring Costello down. Meanwhile, SIU officer Colin Sullivan has everyone's trust. No one suspects he's Costello's mole.