The document summarizes the characters in the 2006 Martin Scorsese film "The Departed". It describes three main characters: Billy Costigan, an undercover police officer infiltrating the Boston Irish mob led by Frank Costello; Colin Sullivan, a mole within the police force who is secretly reporting to Costello; and Frank Costello himself, the Irish mob boss in Boston. It notes that the characters' downfalls stem from their egos becoming too large.