When a young girl is found dead in Seryong Lake, the police immediately begin their investigation. At the same time, three men --- Yongje, the girl's father, and two security guards at the nearby dam, each of whom has something to hide about the night of her death --- find themselves in an elaborate game of cat and mouse as they race to uncover what happened to her. After a final showdown at the dam results in a mass tragedy, one of the guards is convicted of murder and sent to prison. For seven years, his son, Sowon, lives in the shadow of his father's shocking and inexplicable crime. When he receives a package that promises to reveal at last what really happened at Seryong Lake, Sowon must confront a present danger he never knew existed.

Early one morning, 26-year-old Yu-jin wakes up to a strange metallic smell, and a phone call from his brother asking if everything's all right at home --- he missed a call from their mother in the middle of the night. Yu-jin soon discovers her murdered body, lying in a pool of blood at the bottom of the stairs of their stylish Seoul duplex. He can't remember much about the night before; having suffered from seizures for most of his life, Yu-jin often has trouble with his memory. All he has is a faint impression of his mother calling his name. But was she calling for help? Or begging for her life?