Ko Chow (Chow Yun-Fat, Crouching Tiger Hidden Dragon, Hard Boiled) is about to resign from the police force when he is asked to take on one more case. He is to go undercover in a gang that is robbing jewelry stores. He accepts the task and successfully infiltrates the gang. It is a very dangerous mission, not just because the gang might discover his true identity, but because many of the police suspect he may well be a criminal.