In South Boston, the state police force is waging war on Irish American organized crime. Young undercover cop Billy Costigan is assigned to infiltrate the mob syndicate run by gangland chief Frank Costello.
While Billy quickly gains Costello's confidence, Colin Sullivan, a hardened young criminal who has infiltrated the state police as an informer for the syndicate is rising to a position of power in the Special Investigation Unit.
Each man becomes deeply consumed by his double life, gathering information about the plans and counter-plans of the operations he has penetrated. But when it becomes clear to both the mob and the police that there's a mole in their midst, Billy and Colin are suddenly in danger of being caught and exposed to the enemy-and each must race to uncover the identity of the other man in time to save himself.
The question remains, is either willing to turn on the friends and comrades they've made during their long stints undercover? How their respective futures unfold, will depend upon the choices they make and the loyalties they decide to fulfil or betray...
Did you know?
Leonardo DiCaprio was cast in the title role in The Good Shepherd (2006), but he dropped out to play Billy Costigan in this movie. Matt Damon then took the role. Robert De Niro turned down the role of Queenan to appear in The Good Shepherd. Read More