1991 film by Johnnie To

2006 film by Johnnie To

A cop who loses his partner in a shoot-out with gun smugglers goes on a mission to catch them. In order to get closer to the leaders of the ring he joins forces with an undercover cop who's working as a gangster hitman. They use all means of excessive force to find them.

1999 film by Johnnie To

2003 film directed by Andrew Lau and Alan Mak

2003 film directed by Andrew Lau and Alan Mak

Chan Wing Yan, a young police officer, has been sent undercover as a mole in the local mafia. Lau Kin Ming, a young mafia member, infiltrates the police force. Years later, their older counterparts, Chen Wing Yan and Inspector Lau Kin Ming, respectively, race against time to expose the mole within their midst.