A social worker attempts suicide after killing his family, but he fails and behaves madly in the hospital. Ching (Stephy Tang), a forensic psychiatrist with a special power that can see into people's subconscious space performed an appraisal of him. She finds a voice in his subconscious space inducing him to do all kinds of cruel acts.
Ching investigates the social worker's last visited psychiatrist, Doctor Yan (Gardner Tse). She suspected that he is the voice that taught the patient to kill! Ching asks Crime Unit Sergeant Fat (Philip Keung) to investigate. Due to patient confidentiality, Ching cannot provide any evidence.
When the second murder case happens, Fat investigates Ching's childhood and reveals her traumatized past. Fat begins questioning her justice and her motivation.