Star Chow is about to be kicked out of the Royal Hong Kong Police's elite Special Duties Unit. But a senior officer decides to give him one last chance: Star must go undercover as a student at the Edinburgh High School in Hong Kong to recover the senior officer's missing revolver.

Star Chow, an officer in the elite police unit, resigns when he is made a scapegoat for a botched investigation. He goes undercover at a school to complete the case and realizes a bumbling detective is also undercover as a student.

Chow Sing-Sing returns, only this time he doesn’t go back to school. Instead, Chow goes undercover as the husband of a wealthy socialite, which doesn’t sit well with his fiancée, who tries to convince Chow to quit working as undercover.