The story of a man named Yook Dong-sik who coincidentally witnesses a murder and picks up the killer's diary. While fleeing the scene, he gets into a car accident causes him to lose his memory. Due to the diary in his possession, he mistakenly believes that he is a psychopathic serial killer.

Psychopath Diary тривав 1 сезон. Нових епізодів не заплановано.