Psychopath Diary

Yook Dong-sik gets fired from his company for a mistake of his superior. Dong-sik witnesses a murder when he is about to take his own life.

Dong-sik mistakenly believes that he is a psychopath. The real murderer, Seo In-woo, starts to look for his lost diary.

Dong-sik devises a plan to murder Seo Ji-hoon. The work colleagues do not know what Dong-sik thinks. Knowing what has happened, In-woo approaches Dong-sik.

Dong-sik successfully kidnaps Ji-hoon. Dong-sik gets promoted thanks to his work performance being appreciated and recognised in the company.

In-woo and Bo-kyung follow Dong-sik with different motives of their own. Bo-kyung discovers a pattern of serial killing thanks to Dong-sik.

In-woo realises that Dong-sik is working with Bo-kyung to find out the true culprit of his murder cases. Dong-sik feels confused after knowing what happened to Hong Jin-gu.