Two high school students, both new to the same class, meet their end on the same day. The student poised to be the class valedictorian is fatally stabbed on the street, while the runner-up appears to have leaped from the school’s rooftop. The prevailing assumption is that the latter killed his peer before taking his own life. However, when investigators discover small pill boxes inside the stomachs of both teenagers, each containing a confession to the murder, two South Korean detectives find themselves embroiled in a fresh series of homicides. As they pursue the elusive serial killer, more students fall victim…