Hwang Shi Mok is an exemplary prosecutor who suffered from hypersensitivity to certain sounds. After undergoing a brain surgery in his youth he almost lost his sense of empathy. While investigating a strange murder case, he meets police lieutenant Han Yeo Jin, and she assists him in solving it. As they begin to unravel the mystery behind the murders, they also discover that someone guides and someone hinders their efforts to unfold the secrets about a larger scheme of corruption between the government's Public Prosecutor's Office and a private conglomerate.

Detective Cha Young Jin, from the regional investigation unit, has only one thing on her mind to catch the 'Stigmata' serial killer that killed her friend 19 years ago. She has no friends and lives alone. Her downstairs neighbor's son, Go Eun Ho, has built a relationship with her ever since she moved above their apartment. He does menial house chores for her. One day he opens the door of the room he wasn't supposed to. Lee Sun Woo, former chairman's son and current chairman's brother in law, is Eun Ho's homeroom teacher. He feels something is wrong with Eun Ho.

The story of two fearless men who are willing to go through extreme lengths in their pursuit of a returning serial killer. To uncover the murderer's identity, the two are forced to look deeper than what the evidence seems to suggest.

Jung Ba Reum (Lee Seung-gi) is a rookie police officer, working at a police substation whose life changes when he encounters a psychopathic serial killer. This drives him and his partner Go Moo Chi (Lee Hee-joon) to unearth the truth behind psychopathic behaviors. This also raises the questions, whether it is possible to scan a psychopath in the mother's womb using fetal genetic testing? And if the child in the womb is a psychopath, will it be wise to have that child?

An eccentric genius profiler works with a detective with photographic memory and a police chief to go after a serial killer who was thought to be dead.

K-psychos