Tim Sir, Siu Yau, Sam, and Ding Ding are part of the Hong Kong police department that solves murder cases. Sam, the doctor on the team, meets a young girl named Mon, and tries to help her get her life back on track. Also an amateur author for crime novels, Sam shows Mon some of his work, which she ends up enjoying. One day, the police force is called to a very strange case. The murder victims have been killed in the same way the victims were in Sam's books. When the team begins to suspect Mon - they find her dead. Who is this strange serial killer and why are they killing people following Sam's books?