A dismembered body was found in the waterway of a farm. As detectives investigate the scene and found peppermint candy inside the mouth of the dead body, they seem obvious to recall a serial killer from 5 years ago.

While Soo-young requests Hyun-jae to send her to RIU, the suspect turns himself in. The detectives sense that another victim of his may still be alive so they send Soo-young to his hideout.

The culprit Seung-hwan claims himself as the peppermint candy serial killer but soon after he gets killed by a mysterious man in a police officer uniform. Soo-young senses that the suspect is the accomplice and chases after him.

Hyun-jae and another profiler Jun-seok are on the murder list of the serial killer. As Soo-young and Hyun-jae expected, the serial killer sends a message in public that he's still alive by strangling Jun-seok on air.

The press is making a huge issue about the return of peppermint serial killer from what happened to Jun-seok. And Soo-young notices that someone has broken into her house.

The serial killer shows up to Hyun-jae but Hyun-jae unexpectedly takes him down. Meanwhile, Soo-young hears that Hyun-soo is kidnapped by a child sex offender.