Although Baek Hee Sung is hiding a dark secret surrounding his true identity, he has established a happy family life and a successful career. He is a loving husband and doting father to his young daughter. But his perfect façade begins to crumble when his wife, Cha Ji Won, a homicide detective, begins investigating a string of serial murders from 15 years ago. Ji Won notices changes in Hee Sung’s behavior and begins to wonder if he could possibly be hiding something from her.