故事从上世纪七十年代开始。杰克·尼科尔森扮演的黑帮头子科斯特罗正处当打之年，他控制了整个波士顿的街区。年仅14岁的科林成为尼科尔森重点培养的对象。 　　与此同时，另一个少年比利也闯进了他们的生活。比利的父亲在飞机场工作，心地善良。由于拒绝为科斯特罗效劳，被黑势力所迫害…… 　　时光飞逝，科林和比利都已经长大成人。两人都考上了警校，当上了州警察局的警察。但是科林（马特·达蒙扮演）依然听命于黑帮头子科斯特罗，他是警方中的卧底，而比利（迪卡普里奥扮演）则希望当一个好警察，为父报仇雪恨。 　　在成功打入波士顿有名的黑帮团伙——昆南，并一举歼灭之后，科林获得了嘉奖并提升。 　　与此同时，科斯特罗的势力越来越大。警方已经了解到，内部也出现了黑帮卧底。遂决定派遣比利扮成黑帮分子前往调查。 　　随着时间的推移，敏感的科斯特罗也觉察到了身边出现了警方卧底，于是警方和黑帮都决定展开洗底行动…… 　　The Departed has been hailed as director Martin Scorsese's most powerful film since Goodfellas. With critical acclaim, major stars and all the punch of an explosive crime drama, The Departed is set to be a box-office smash. The soundtrack album features songs from all-time greats The Rolling Stones, The Beach Boys, The Allman Brothers Band, Roy Buchanan and Badfinger along with a collaboration between Pink Floyd's Roger Waters, Van Morrison, and The Band. Add cult faves The Human Beinz, current South Boston punkers Dropkick Murphys, an R&B gem from LaVern Baker, a country- pop selection from the immortal Patsy Cline, and a pair of selections from Grammy?? Award-winning score composer Howard Shore and The Departed's soundtrack album promises to be as widely popular as the film.