Ng Ah Chow (Richard Ng) and Beethoven (John Sham) are two policemen. They have been friends for years and gave lived together in the same flat. Now that Ng is getting married with Anna (Deanie Ip), Beethoven has to move to another flat. He is a very simple-minded person and due to his carelessness, always causes trouble for his tenants. Chan is their head for years. But now they are being transferred to another department headed by the fearsome Tien. Their first assignment is to track down an informer, which they fail. Chan is to deliver an amount of $200,000 as court evidence for a case. The money is switched during a fake accident performed by "The Flying Spider" and his daughter Mimi, alias Yuen Hung. Spider was arrested by Chan 20 years ago and got a broken leg accidentally. He hates Chan for this and swears to revenge. Chan will be facing imprisonment. Both Ng and Beethoven agree to track down Spider for him. They find out that Spider worked in a film studio. Beethoven meets Mimi at the studio, falls in love with her almost immediately, without knowing that she's Spider's daughter. Ng finds out the secret and ruins their relationship. Beethoven is mad with hin but when he finds out the truth, decides to act as mediator between Spider and Chan. All of them set up a trick in which they will return the money to the court and also avenge Chan for Spider, without even injuring or killing anyone. It is going to be a HAPPY ending.