On the day the 15-year statute of limitations expired on a high profile serial murder case that claimed the lives of 10 women, a family member of the victim throws himself off the building in front of Choi Hyeong-goo (Jung Jae-young), the detective in charge of the case. Two years later, a man called Lee Doo-seok (Park Si-hoo) publishes a book titled "I am the Murderer" claiming responsibility for the murders that took place 17 years ago. His book becomes a bestseller because of the author’s charming looks and his vivid depiction of the crime. The detective and the self-proclaimed murderer meet face to face on a television debate show. Believing that Lee is nothing but a con artist, Detective Choi renews his search for the ultimate truth. Then another man appears suddenly, claiming he is the real killer.