A Hongkong action movie about undercover cop Muscles (Jackie Chan) enlists his childhood friends, the "Five Lucky Stars", to travel to Japan to help him catch a Yakuza group-an ex-cop who stole a large amount of money in diamonds. After one is caught by the Ninja-gang protecting the evil cop, the other one gets his old Orphanage gang, dubbed the "Five Lucky Stars," to help him. They don't like this much, but they do it.