Detective Yousuke Kobayashi is chasing a serial killer who dismembers his victims when the case turns on him: his girlfriend Chizuko is mutilated and left alive, and a second personality, the cool-headed criminologist Kazuhiko Amamiya, surfaces to take his place. Diagnosed with dissociative identity disorder, Kobayashi finds that each personality reads a crime scene differently. What began as one murder investigation opens onto a chain of killings and a conspiracy far larger than any single case.