In 1998, a five-member gang called "Baek Mei" led by Seok-tae (Kim Yoon-seok) kidnapped the young son of a powerful person. After the operation failed, they did not kill the boy, but adopted him as their son and consciously trained him to be a killer successor. Nearly twenty years have passed, and the boy named Hua Yi (Yeo Jin-yeol) has grown up and become a handsome high school student. Seok-tae committed a series of vicious crimes in accordance with the instructions of his superiors. He intended to let Hua Yi step into this path, but the boy seemed to have the ability to see monsters since he was a child, so that he always failed at the critical moment. During a certain operation, Hua Yi accidentally learned the mystery of his life experience, but Seok-tae had to shoot at the man who was related to him by blood. Seok-tae, who was stubborn, was increasingly dissatisfied with the superior organization, and the police officer who was always tracking down Bai Mei. Hua Yi's fate was caught in a vortex...