The drama is about a psychopath who changes his identity to hide his dark past, and his detective wife, who tries to find out the truth after learning about the deception.
Baek Hee Sung (Lee Joon Ki) is a metal craftsman. Thanks to his workshop, he makes enough money to provide for his wife and daughter and show his dedication as an exemplary husband and father. Hee Sung is a family man who is good both in housekeeping and in raising a child. He is not greedy and is content with what he already has. However, But this perfect exterior hides some very dark secrets. Secrets he would rather his detective wife, Cha Ji Won, never learns.
Cha Ji Won (Moon Jae Won) is a detective at the violent crime department. Although her tiny height and baby facial expressions may raise questions about whether she can cope with violent crimes, but when she finds herself in dangerous situations, her curiosity excites her more than fear. The excitement that she receives from solving crimes gives her great satisfaction from her work.