Baek Hee Sung and Cha Ji Won are a married couple with a daughter. Ji Won is a detective and investigating a case in which In Seo, a boy, got into an accident and pointed his father as the culprit.
A murder case similar to the Yeonju City serial murder case happened. The victim's thumbnail was missing. Something seems off about the case and Ji Won tries to solve it.
Ji Won feels something is not right when she saw Hee Sung coming home with a raincoat on in the middle of the night. Ji Won gets assigned another murder case, surveillance footage shows that the victim got killed by a man in a raincoat
Hee Sung gets baffled to become the prime suspect of Hoesin-dong Chinese restaurant murder case. Only Hee Sung and Moo Jin know that someone else is copying Do Hyun Su to pin the murder case on him.
A police officer hands over a watch strap that is engraved with Hee Sung's initial on it. Ji Won instinctively feels something is wrong. And the owner of the inn calls the police to report that a taxi driver is beating up a passenger.
Hee Sung was brought to an emergency room without any consciousness. Luckily, he wakes up, but Ji Won heard something unexpected while Hee Sung was unconscious. Moo Jin tries to talk to the witness to get to the bottom of the story.
Ji Won can't clear up her doubts about Hee Sung, so she triggers him with the recording of Do Hyun Su's voice and asks him to go to Do Min Seok's workshop. Hae Su meets up with Moo Jin.
Hyun Su asks Moo Jin to look for Hae Su in order to find the accomplice. Ji Won's team gets to re-investigate the Yeonju City serial murder. Meanwhile, Hyun Su finally meets Hae Su.
Ji Won visits Moo Jin's house and finds Hyun Su and Hae Su there. Ji Won tells Hyun Su that she doesn't love him anymore. Hyun Su thinks the only way to turn things back to normal is to find the accomplice himself.
Hyun Su seals a deal with the head of the human-trafficking ring to retrieve information about Do Min Seok's accomplice. Ji Won feels anxious about Hee Sung's every move and Hee Sung starts to think that Ji Won might know who he really is.
Hyun Su gets into trouble while undergoing a plan to find Do Min Seok's accomplice. Just when Hyun Su is about to give up, Ji Won shows up and saves him. Although Ji Won forces Hyun Su to run away before it's too late.
