Bumbling Hong Kong detectives Lui (Kenny Bee) and Leung (Tony Leung Ka-Fai) go undercover in an apartment complex to keep watch over Pearl Chan (Carina Lau), a high school teacher who is suspected to be connected to a rare diamond theft involving a notorious thief named Mr. Mickey (Simon Yam). Meanwhile, the legendary Black Rose (Veronica Yip) appears and is also in pursuance of Mr. Mickey, wanting him to surrender himself and the diamond in order to clear her name.