Super-soldier recruit Tsui Chik is forced to escape with his comrades after the project is canceled. Months later, he's trying to have a quiet life as a librarian with his best friend, Inspector Shek Wai-Ho. However, a string of vicious gangland murders begins that has all the markings of Tsui's former compatriots who seem to have turned to crime. Realizing that the police are helpless, he decides to take them on himself. With a disguise, Tsui becomes the mysterious superhero known only as Black Mask.

Four young officers of the Hong Kong Police are joined together to fight against organised crime using all possible means, even if this would lead them to break the law… Their first assignment is to eliminate a gang of criminals who have stolen a shipload of explosives.