A young American nicknamed "Buffalo" visits his uncle, a police officer in Hong Kong, to find a wife. His uncle does everything he can to help him. But fate brings Buffalo together with a thief who accidentally witnessed a murder and took a ring with her. A mafia boss desperately needs this ring, which serves as the password for a major deal. But Buffalo can’t stand injustice, and he’s also taken a liking to the girl.

Francis, an unlucky police sergeant, is jokingly nicknamed "Tiger" by his colleagues. Together with his new partner, Michael, he must investigate what appears to be a routine gangster murder. But the case takes an unexpected turn.