Connected by phone in the same home but 20 years apart, a serial killer puts another woman’s past — and life — on the line to change her own fate.

As a result of a traffic accident involving a violation of the centerline, the perpetrator dies, and the victim falls into a coma. After some time, the wife of the perpetrator, Heejoo, returns. Heejoo is bewildered at the fact that the victim’s wife Youngnam is also working at the factory where she goes to work. By accident, Heejoo becomes close with Youngnam’s daughter Eunyoung and learns a new fact about the incident. The true nature of this accident, where Heejoo’s husband was known to have crossed over the centerline, is actually very complicated. Since the social issues of dispatched labor and industrial accidents and personal issues of depression and family trouble are intertwined here, it is more difficult to apprehend.