Sung is a photo lab technician. He has a good nature and doesn't stick his nose in other people's business. King, by contrast, is the embodiment of evil: a powerful triad boss who is guilty of all the crimes that are under the sun. Sung and King don't know each other, but a bottle of deadly cyanide brings them together. King's death sends shock waves throughout the city. The triads are looking to take over his business while the police try to track down the killer. Michael is the detective who comes to the case with mixed feelings. Despite his professional duty, he is happy to see King dead and hopes whoever killed him can escape prosecution. The deaths of other Triad members soon add confusion to Michael's investigation. For Sung, murdering King has sparked his desire to root out all evil in the city. Imagining himself as a warrior battling evil, he plots his vigilante killings in an obsessive yet playful manner.