Detective Dee (Mark CHAO) is appointed by Emperor Gaozong to protect the Tang Dynasty from rival Empress Wu (Carina LAU) and is bestowed with the magical Dragon Taming Mace. Wu orders Yuchi Zhenjin (FENG Shaofeng) of the Golden Gard to recruit five mystics and task them with stealing the threatening Mace, the consequence of which is capital punishment for Dee.
Storming the Department of Investigation, Wu orders a demonstration of sorcery power which goes horrifically wrong with deadly consequences. In the confusion, Yuchi Zhenjin is seen killing colleagues of the Golden Gard. It falls to Detective Dee to solve the puzzle and redress the balance of power to save the Tang Dynasty.