Dr. Ko Lap-yan heads a team of senior psychiatrists and residents at the Yan Wo Hospital in Hong Kong. Most episodes revolve around the team diagnosing patients. With a specialty at diagnosing criminals, Ko also has close ties with the Serious Crime Unit of the Hong Kong Police Force, a unit headed by Senior Inspector Chung Kwon-ban. The second series sees Ko's resignation from the Yan Wo Hospital; he is later transferred to a new psychiatric department, the Forensics Psychiatry Department, of Bok On Hospital, where he formally diagnoses criminals.