 In a province in China, Detective Ma Shan wakes up on the day after the wedding party of his sister Ma Juan and finds that his gun with three bullets is missing. Ma Shan drank too much in the party and does not recall what might have happen with his weapon. He falls in disgrace with his superiors and investigates who might have stolen the gun. When his former sweetheart Li Xiaomeng is found dead with a shot of his weapon, he becomes the prime suspect. When the police force arrests his acquaintance Zhou Xiaogang, he discloses that Li Xiaomeng was accidentally killed since his friend was the real target of the murderer. Ma Shan uses Zhou Xiaogang as a bait to lure and arrest the criminal an retrieve his missing gun.