When Kim’s husband John raves about a new co-worker named Grant, she’s shocked to discover upon meeting him, that it’s her ex-boyfriend. While they try to keep their former relationship a secret, John starts to suspect an affair and accidentally kills Grant in a fit of rage. Worried they’ll be implicated in murder, Kim directs John to impersonate Grant in a desperate cover-up that spirals into obsession.

Ji-su who has a borderline personality disorder feels a strange emptiness and tries to commit suicide. At the hospital she meets a psychiatrist, Suk- won. Suk-won feels compassion for her but fails to give her any help. 1 year later, Suk-won accidentally meets Ji-su and finds out that she still needs help. This time, they start to meet not in a doctor/patient relationship but as friends. In this new relationship with Suk-won, Ji-su slowly starts to cure the deep wound from her past. However, Suk-won is too much into Ji-su and now, he can’t live without her. His obsession for Ji-su becomes so extreme that when Ji-su decides to leave him, his love drives him to a dangerous edge.