A crooked new police chief causes trouble for the team. The deaths of a professor and his wife touch off a series of brutal murders.

Yoon Tae-gu and Kim Bong-sik seek to set boundaries on the behavioral analysis team. A complex investigation sends the police down a twisted path.

Ha-yeong spends time with his mother on his birthday. With two killers on the loose, the investigators are faced with high-pressure stakes.

The behavioral analysis team agrees to an interview with a journalist. Ha-yeong seeks to enter the killer’s mind, but it takes a toll on him.

During interviews and crime scene reenactments, Ha-yeong and the police dive deep into a ruthless suspect's psyche and past trauma.