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……Supt. Nancy Ho (Sylvia Chang) is kidnapped by villains who want to obtain a hi-tech prism, created by a Hong Kong professor, that can grant superhuman powers. In exchange for Supt. Ho's return, King Kong (Samuel Hui) and the professor's daughter Sally (Sally Yeh), later joined by Albert "Baldy" Au (Karl Maka) and Baldy Jr. (Cyrus Wong), fly to New Zealand to deliver the hi-tech prism to the crooks. However, not allowing to let the crooks succeed, they must band together to prevent the prism from being used.