Hahou Mo, a martial arts expert from police force is arrested for involuntary manslaughter during a battle with an opponent. Three years later, a ruthless killer appears and begins murdering retired martial arts masters that Hahou knows. With his long-based relationships and knowledge in the field, Hahou states that he knows the murderer's next targeted victims and proposes to support Inspector Luk Yuen-Sum in hunting down the killer in exchange for his freedom.