Scorsese goes back to the mob (Irish and in Boston this time) for a complicated and violent tale of identity and betrayal based on the Hong Kong flick "Infernal Affairs." Colin (a strong Damon) is a state police officer who's actually a mole for crazy kingpin Frank Costello (Nicholson, nuttier than ever) while jittery Billy (an equally strong DiCaprio) is the cop who's infiltrated Costello's gang at the behest of his tough bosses Queenan (Sheen) and Dignam (Wahlberg). Both younger men are involved--in different ways--with lone femme, shrink Madolyn (Farmiga). Tension builds, insults and bullets fly, and the truth will out--with some unexpected consequences. Scorsese's at his best (if in familiar territory).