Through an unseen, incredible connection, an old phone connects over time between Seo-Yeon, who lives in the present, and Young-Sook, from the past. Young-Sook was raised by a stepmother, a shaman, who, having the ability to see the girl’s future, kills her following an exorcism ritual, unaware that the girl had a mental illness and was not possessed, as she believed. Seo-Yeon, with the help of the past, saves his father from death and feels obliged to save Young-Sook’s life. It’s just that the girl’s mental illness from the past is getting worse, and the first crime committed in self-defense awakens the murderous instinct in her. He quickly realizes the advantage that the phone offers him and the power he has over Seo-Young, being able to control, from the past, the future in his interest.