The series is about Noh Ji-wook (Ji Chang-wook), a prosecutor, and Eun Bong-hee (Nam Ji-hyun), a prosecutor trainee, and how they work together on a mysterious case involving a sly psychopath murderer. They find out how deeply connected they are by their past. A forgetful killer can be a dangerous thing. Noh Ji Wook (Ji Chang Wook) is a prosecutor who changes jobs to become a private attorney at a powerful law firm. Eun Bong Hee (Nam Ji Hyun) is a prosecutor trainee who works with prosecutor Cha Yoo Jung (Nara), Ji Wook’s ex-girlfriend who desperately wants to win him back. Attorney Ji Eun Hyuk (Choi Tae Joon) is a longtime family friend of Ji Wook’s but harbors some resentment about their different family circumstances.
When a murderer strikes, Bong Hee suddenly finds herself as a suspect in the murder. But it appears the real killer has amnesia, and the killer keeps coming after Bong Hee and Ji Wook.