A serial killer organization called "The Night Watch." The members of this organization are not murderers in the traditional sense. They aim to "trial" evildoers who cannot be punished by law. They use clever methods and clean up the scene extremely cleanly. They have repeatedly challenged the police and forensic doctors. In the process of confronting him, the protagonist Chen Mo gradually discovered that his late mentor, a well-respected old forensic doctor, seemed to be inextricably linked to the "Night Watch".
