A police informant sent a letter containing sensitive information on an illegal drug operation to his friend, Yi-Ching. While on vacation in Thailand, the informant is assassinated by the drug lord's henchmen and, to cover-up their operation, they attempt to eliminate Yi-Ching and double-agent Lau. Back in Hong Kong, police detectives Muscles and Ricky Fung are assigned to protect Lau and Inspector Barbara Woo is assigned to protect Yi-Ching. She takes her to the hideout of the "Five Lucky Stars" and also enlists their help in bringing down the drug operation.