Oh Hyun Jae used to be a top criminal profiler. He solved many cases with his skills, but one day an explosion, caused by a serial killer, ended the life of his fiancé. After the horrific incident, Oh Hyun Jae vanished and he now lives in seclusion. Meanwhile, Cha Soo Young is a police officer in the countryside. She has a special ability which allows her to remember exactly everything she sees. Due to her special ability, she is selected as a rookie detective who will partner with Oh Hyun Jae informally. Together they work to solve cases and uncover the truth behind the Peppermint Killer, the resurfaced serial killer who murdered Hyun-Jae's fiancé five years ago.