The series revolves around Yook Dong-Sik (Yoon Si-Yoon), who witnesses a murder and loses his memory in an accident while fleeing the crime scene. After witnessing the murder, Yook Dong-Sik accidentally comes into possession of the killer's diary, which records the crimes committed. While escaping with the diary, he has an accident and loses his memory. Due to his amnesia, Yook Dong-Sik cannot remember anything about his identity and believes he is the killer because of the diary he holds.
