Twenty years ago, Moo-father Yeom's was a suspect in the "Gap Dong" case, which involved a string of murders. Because the detectives' investigation was so stressful, Moo-father Yeom's ended his own life. Now, Moo-Yeom works as a detective to catch the murderer Gap Dong. The time limit for the serial murder case has passed, so Moo-Yeom gives up and accepts that Gap Dong is dead. Moo-Yeom gets new information about Gap Dong, and he sets out to catch him for good.