Nearly 20 years ago, Ha Mu Yeom's father was a suspect in the Gap Dong serial murder case in Iltan, and the primary focus of detective Yang Chul Gon. Mu Yeom becomes a detective to try to solve the Gap Dong case but the statute of limitations expires. However, graffiti at a mental hospital in Iltan with claims about the real Gap Dong reintroduces the case. Chul Gon returns to Iltan as the chief and puts pressure on Mu Yeom, believing he was complicit in his father's crimes.