Jang-woo and Eun-ji are orphaned siblings living in a small seaside town. They are very close, having only each other to rely on after their parents passed away. Jang-woo is saving up to move to the city so that his younger sister Eun-ji will have better opportunities once she graduates from high school. But one day Eun-ji suddenly disappears, and she turns up dead three days later, her body bruised all over and dumped in a large bucket of water at their washhouse. No witnesses and evidence to the crime can be found. Jang-woo turns to shamanism, but during the ritual to send Eun-ji's spirit to heaven in peace, he notices a suspicious man and takes the latter's behavior as Eun-ji's hint from the afterlife to find her killer.

Si-eun has been ostracized by the townspeople for her mysterious psychic ability to foresee death. She received a premonition of the death of her only friend Eun-ji, but stayed silent. Now wracked with guilt, Si-eun approaches Jang-woo to help him with the clues in her vision. She saw fragmented images related to the murder, but not the face of the killer. The duo begins tracking down a number of other murder cases suspected to have been done by the same person. Then Si-eun sees premonitions of the next target, and Jang-woo goes to the location where she predicts the murder will take place to catch the perpetrator. There, he encounters Pharmacist Min, known as the kindest person in town. Jang-woo becomes absolutely certain that the pharmacist is the serial killer, but the police refuses to investigate Min due to his upstanding reputation. Obsessed with avenging his sister, Jang-woo decides to take matters into his own hands, while Si-eun has another vision of the next murder.