Baek Hee-sung is a man who hides his identity and past from his wife Cha Ji-won, a detective. On the surface, they appear to be the perfect family: A loving couple with a beautiful six-year-old daughter who adores her parents. Cha Ji-won and her colleagues begin investigating a series of unexplained murders and she is confronted with the reality that her seemingly perfect husband may be hiding something from her.