On a certain rainy night, Lok Ka-kei, the only daughter of Lok Yat-yin, an inspector from the Criminal Investigation Unit of the Macau Judiciary Police, was found dead in the outskirts. Based on the semen and DNA found in the victim's body, the police arrested Yau Chun-man, a classmate of Lok Ka-kei. After the death of his daughter, Lok Yat-yin left the police force dejectedly. He thought it was all over. However, a month after the suspect was sentenced to prison, several girls were brutally murdered one after another in Macau. Lok Yat-yin began to suspect that the real culprit who killed his daughter was still at large.