The rivalry between two Chinese prison factions heats up as a seasoned inmate forms an alliance that could cost him more than his freedom.

纽西兰老科学家发明一个名为“天狼星”的三棱镜，它可将人的潜能激发，形成难以置信的超能力。但这项发明很快被当地一黑社会组织盯上，他们袭击实验室，杀害老科学家。危急时刻，天狼星被参加实验的青年金刚（许冠杰 饰）和科学家的女儿莎莉（叶倩文 饰）带出纽西兰，来到香港。 返港后，金刚寻求侦探光头佬（麦嘉 饰）的帮助，谁知黑帮尾随而至，虏走光头佬的妻子贺警司（张艾嘉 饰）作人质。为救爱妻，光头佬带着儿子，协同金刚赶至纽西兰……

Twins, separated at birth, end up as a Hong Kong gangster and a New York concert pianist. When the pianist travels to Hong Kong for a concert, the two inevitably get mistaken for each other.

Former cop-turned-bar owner Kwok and his underachieving half-brother befriends a drunken woman, they soon find themselves targeted by both her former lover, a high-powered attorney, and the gangster he employs. A suitcase full of tainted cash enters the picture as Kwok finds himself torn between the gangsters and his former colleagues.