全城戒备

马戏团正在马来西亚巡回演出，传说二战时期日本人在这里留下了宝藏，团员们准备寻找这个宝藏。桑尼（郭富城饰）是马戏团的小丑，他偶然尾随飞刀高手张大初（邹兆龙饰）时，意外看到他们杀害了寻宝者，目睹一切的他被张大初抓住，被迫一起去寻宝。一行人无意之间开启了日军留下来的生化武器，他们误吸后肌肉骨骼开始变化，出现了类似狼人一样的兽化，桑尼因为身手矫健吸入的最少，但是却有其他的变化一会变成肥佬，一会却面部全非。

几个变成狼人的张大初来到香港，引发数起抢劫案件，警察发现行凶者赤手空拳但是手段极其残忍，警方觉得这个案件太过诡异恶劣，于是请来了内地高手孙浩和程秀华协助调查，桑尼阴差阳错的拥有神秘力量，成为收拾罪犯的关键。

The circus is touring in Malaysia. It is said that the Japanese left treasures here during World War II. The members are going to find this treasure. Sonny (played by Aaron Kwok) is a clown in the circus. When he accidentally followed the flying knife master Zhang Dachu (played by Collin Chou), he accidentally saw them kill the treasure hunters. He was caught by Zhang Dachu who witnessed everything and was forced to go treasure hunting together. . A group of people inadvertently turned on the biochemical weapons left by the Japanese army. After they inhaled by mistake, their muscles and bones began to change, and a beast like a werewolf appeared. Sonny inhaled the least because of his vigorous skills, but there were other changes. Become a fat guy, but after a while, his face changes completely.

Several Zhang Dachu who turned into werewolves came to Hong Kong, causing several robberies In this case, the police found that the assailant was unarmed but extremely cruel. The police felt that the case was too weird and bad, so they invited mainland experts Sun Hao and Cheng Xiuhua to assist in the investigation.