Seo-jin (GIM Mu-yeol) is a successful architect but suffers from several traumas. When he was a child 25 years ago, his sister suddenly disappeared, and more recently he lost his wife in a car accident. As he undergoes hypnosis as a form of therapy, Seo-jin sees his long-lost sister You-jin (SONG Ji-hyo), and low and behold, soon after that she returns to her family 25 years after her disappearance. However, Seo-jin can’t help but feel that something is not quite right about this woman and he begins to doubt that she is actually his sister, though no one listens to him. When he undergoes hypnosis again, he sees this woman once more, but beside the site of his wife’s car crash. Now it is imperative for him to find out who she is.