This intriguing thriller tells the story of a small-town policeman, Ma Shan (Jiang Wen), who discovers one morning that his gun is missing. In China, where guns are extremely rare, this is serious business; an official who loses his gun can be sent to prison. Ma Shan fears the gun's absence is not accidental, and that whoever has it plans to use it. First on the list is Zhou Xiaogang, the richest man in town as a result of shady business deals. Reaching Zhou's house, he is shocked to find the door answered by Li Xiaomeng (Ning Jing), Ma Shan's long-lost first love. When Li Xiaomeng turns up dead and the bullet appears to be from Ma Shan's gun, Ma Shan is arrested for murder. To catch the real killer, he must lay a trap that will be just as dangerous for Ma Shan as it is for the criminal.