One day, an abnormally murder happened again in the dark side of the street. The victim’s tongue is cut. The police are busy for those consecutive cases, but it doesn’t cause any feedback from the people in the street. Especially for new comer Ah Wa, she just arrived in Hong Kong, but she will be involved later. There are 3 people come to pick up her on that day, they are Uncle Chai, Ah Ting & Ah Tai. On the way to home, several guys show up suddenly to seize Ah Tai. Ah Wa save her friend with violent fighting with them. After that, Ah Wa know these guys originally compel Ah Tai to repay her own debts, Ah Wa then promise to take over the responsible to pay back her outstanding, and invite Ah Tai to live with her together. But Ah Tai does not care their giving to steal all their belongings, Ah Ting & Ah Wa finally meet her again, but she go away by chance. Nobody know she is chosen by murderer. Her body is found later. As Ah Ting & Ah Wa are witnessed have an argument with Ah Tai before, they are suspected to kiss Ah Tai. In order to prove themselves innocent, they ask for help with uncle Chai. They act as a police in causal wear to investigate the matter and cause a substantial of jokes.