Detective Sergeant of Serious Crimes Unit, Jun (Donnie Yen) detests crime and his life long nemeses, a Vietnamese gang of three brothers - Archer, Tony and Tiger. In order to further infiltrate the gang and fight them from within, Jun has planted a mole, Wilson (Louis Koo), who has managed to gain the complete trust of the gang. Eventually, Wilson's dual role is exposed and resulting battles leaves him handicapped for life. The day before Tiger's trial, Archer turns up at the hospital to wipe out their only witness, Wilson. Jun manages to kill Archer and protect Wilson but Wilson's girlfriend (Fan Bing Bing) is held hostage by the gang.