The Qiyifang Circus is touring Malaysia, and the members accidentally heard about the treasure left by the Japanese during World War II. Led by the knife master Zhang Dachu (Zou Zhaolong), the five of them killed the treasure hunters. Sunny (Aaron Kwok), a small figure who wanted to become a knife expert, followed and witnessed the whole process of Dachu's murder. He was forced to go down the cave with everyone, but he had no intention of opening the biological weapons left by the Japanese army. After an unimaginable hardship, Sunny escaped by chance, but became a strange look. At the same time, several robberies occurred in Hong Kong. The perpetrators were unarmed and cruel. They were Zhang Dachu and others who were infected by poison gas and mutated. This series of events shocked the whole of Hong Kong, and the police invited masters Sun Hao (Wu Jing) and Cheng Xiuhua (Zhang Jingchu) from the mainland to assist in the investigation. And Sunny also transformed himself into a messenger of justice against evil...