Mingyu and Wonwoo work as detectives in the Homicide Department. With their special skills, they are assigned to a case they already know. A gruesome serial killer who has never been caught resurfaces, and they have little time to solve the case. Jisoo and Jeonghan form a task force to solve the case and find te killer this time once and for all.

  After a car accident during their promotion, Mingyu and Wonwoo have to recover in a rehab center.  Two strangers show up and Wonwoo learns about his dark side. But this side is dangerous, and the two stumble right into a war between two clans...      

Hitman Wonwoo gets a job to eliminate a target. But this job suddenly turns into a rescue mission, and he has only a short time to get the target to safety. And for the first time in his life, that target has a name. And that name is Kim Mingyu.