In just 3 days, three cases of Smiling Murder disturb Hong Kong. Young detective Wang Bu Er, the police station's reckless buffoon, makes a shocking statement that this is a serial murder. He and his buddy Huang Fei Hong set out an investigation full of excitement and unexpected outcomes. After discovering all the victims were former boyfriends of budding actress Liu, the two troublemaking cops (one now posing as her lover) are found in a mortal game to decoy the killer.