Ah Chau and Beethoven are a pair of cops investigating a drug lord, but their ineptitude threatens to derail the case. The police are well aware that Mr Sha is the boss of the crime syndicate smuggling and trafficking in drugs, and that he keeps details of his criminal transactions in a book which is kept by his mistress. When Beethoven and Ah Chau investigate, they find Sha's mistress dead, and inadvertentlycompromise all fingerprint evidence in the hideout. Luckily, they are assisted by beautiful cop Inspector Anna, who is secretly attracted to Ah Chau. Finally the two make their arrests and become instant heroes.