After a run of solid, adventurous but ultimately underwhelming efforts (Gangs of New York, The Aviator), director Martin Scorsese returned to more familiar form with a superior, Boston-set cops-and-gangsters story based on the Hong Kong crime drama Infernal Affairs, and won the long-awaited best director Oscar for his trouble. Rookie cop Billy Costigan (Leonardo DiCaprio) is assigned to go deep undercover to help catch local Mafia godfather Frank Costello (Jack Nicholson). Meanwhile, Costello has groomed Colin Sullivan (Matt Damon) since puberty to be his spy on the force. The complex script (fluently adapted by William Monahan) rotates around these two moles, who orbit each other like twin suns for most of the movie, but only meet in the third act. It all makes for extremely watchable entertainment. The leads are luminous (especially Nicholson, doing his best work in years here), but supporting players Mark Wahlberg, Alec Baldwin and Ray Winstone all steal scenes with glee.