Hung Tai Kong aka 'Rice Pot' (Sammo Hung) and Chan Yin Tung aka 'Chimney' (Frankie Chan) are two brothers who work with their master Kam Ming (Lau Hak Suen) and his daughter Ann (Didi Pang) as a team of pickpockets. Rice Pot, Chimney and Ann later meet Inspector Ling Ah Nam (Deannie Yip), who investigating a diamond robbery and later becomes Rice Pot's girlfriend. She tells Rice Pot that she has to leave for 2 to 3 months. He found out that she lied to him, and later she explains to him and reveals that she is on an undercover mission. Ling asks the three of them to help her snatch a box of diamonds from Chow Ming Shing (Peter Chan Lung).
Later, troubled cop Ng Heung Kan (Richard Ng) runs into Rice Pot and Chimney. Finding out that they are pickpockets, Ng becomes desperate to arrest them.
After successfully getting the diamonds, Ling has them pretend to give Chow the diamonds in order to arrest Chow. However, the diamond that Ling gives them are fake and the three of them become suspicious of Ling. Later, a big fight takes place on Chow's ship and a final fight with Rice Pot against one of Shing's henchmen (Dick Wei).
Ling attempts to flee from Hong Kong with the diamonds and the three of them finds her in the airport. Rice Pot manages to snatch the diamonds from her, only to run into Ng, who was patrolling there which causes him to drop them.
In the end, there was an epilogue for everyone. Rice Pot, Chimney and Ann were charged with theft and mistake of murder. They were sentenced to 7, 5 and 3 years to prison respectively. Kam was charged with theft and receiving stolen goods and sentenced to 2 years. Ling was charged with impersonating a cop and cheating, and was sentenced to 10 years. Sergeant Ng discovered an international criminal group and was promoted to police inspector.