Summary: At a house in Daebong-dong, Gwangjin-gu, a woman was found dead with all of her clothes undressed. When everyone focuses on physical evidence, Ha Young is curious to find out why those criminals commit such hideous crimes. Meanwhile, Young Soo, the chief of Forensics Squad, sees the potential in him and wants to create a new team with him which analyzes criminals' behavior.

Summary: Ki Hoon gets arrested for murdering his girlfriend, and the Daebong-dong case is finally closed. However, Ha Young cannot let go of this case, as he believes that the real culprit is still out there, committing another crime. Therefore, he visits an inmate he met at his station and interviews him to study the minds of criminals. Meanwhile, Captain Park is not happy with him since he is going after the case he has already finished.

Summary: A five-year-old child was murdered in such a hideous way, and the Special Crime Squad is having a hard time because they don't have a suspect. Meanwhile, Ha Young and Young Soo go on the first interview of an inmate together, and he happens to be a mutilation murderer. Since Ha Young is confident with his analysis, he wants to help the Special Crime Squad but, Tae Gu finds them unreliable just like everybody else.

Summary: Behavioral Analysis Team and Special Crime Squad join hands together and search for the missing body parts at Cho Hyun Gil’s home. Even though Ha Young and his team had helped in identifying the culprit, they are still struggling to get noticed by their superiors and peers. However, Ha Young and Young Soo continue to interview criminals for their analysis.

Summary: Ha Young and Young Soo begin interviewing Cho Hyun Gil. However, the more they look into his evil mind, the more confused and frustrated they become. Meanwhile, an elderly couple is found brutally murdered in Gangnam. Another murder occurs in Jongno with a similar MO, and the police start to piece things together.

Summary: Ha Young and Young Soo continue to search for the suspect of elderly murder cases. However, Bong Sik, who has an ugly history with Tae Gu and Ha Young, meets them again as a new chief of Special Crime Squad, and he wants the Behavioral Analysis Team to stay out of this case. Meanwhile, another similar murder occurs in Hwanghwa-dong, and Ha Young visits the crime scene.

Summary: More brutal assault cases occur where the killer only attacked young women with a camping knife. When Tae Gu believes that he is the same culprit for the murder cases of the wealthy senior citizens, Ha Young is certain that both cases are clearly different from one another. Therefore, he announces that there are two serial killers in this country, but the Special Crime Squad doubts his statement again.

Summary: Young Chun gets arrested, but he attempts to run away and even stabs Tae Gu in her stomach. Ha Young realizes that he is different from other criminals, and therefore, he thoroughly observes him and analyzes his mind. However, the more Ha Young studies him, the more he cannot stand how shameless he is even though he committed serious crimes.

Summary: After four years of hard work, the Behavioral Analysis Team finally gets recognized by the higher-ups and the public. The detectives from different police stations even want to learn about Ha Young's profiling analysis on the culprit of the Southwestern Case. However, when Ha Young tries to think like a murderer to solve the cases, Young Soo realizes that he acts like one of those monsters.

Summary: Ha Young gets to interrogate Ki Tae first. He manages to make Ki Tae confess through his listening and questioning technique which allows the suspect to share his personal stories. However, the more Ha Young listens to Ki Tae’s brutal murders in detail, the more he cannot stand his madness. Meanwhile, the police cannot find his weapons which is the supporting evidence to charge him for his crimes.

Summary: Young Soo feels sorry for Ha Young as he has completely drained out from handling serial murder cases ever since he joined the Behavioral Analysis Team. Ha Young cannot take the wickedness of the murderers anymore and decides to resign. Meanwhile, similar missing cases happen in a row for months, and Dae Woong asks for Ha Young’s help.

Summary: The investigation headquarter of Gyeonggi Agency arrests the prime suspect of Missing Women Cases, but they struggle to find the evidence. Furthermore, he is way too calm and confident during the interrogation with the detectives as if he is innocent. Meanwhile, Ha Young discovers his weakness and changes his interrogation tactics to make him confess.