In Seoul, a serial killer known as the Copycat is at work, killing his victims using the same methods they used to kill their victims. Inspector Lee Su-in, the only one who knows his identity, lost his memory and became blind after a fire. Detective profiler Han Jisu is sure the Copycat killed the suspect she interrogated—and only Lee Su-in can prove it. Now she must help the inspector regain his memory in order to catch the murderer.