Shugo Hayami is a doctor at a nursing hospital, which was once a psychiatric hospital. One evening, when Shugo Hayami is on night duty, a man in pierrot mask breaks into the hospital and he is not alone. He is with Hitomi Kawasaki. She is a university student and she has been shot by the masked man. The masked man tells Shugo Hayami to treat Hitomi Kawasaki. He also takes hostage the 64 people in the hospital. Soon, Shugo Hayami and Hitomi Kawasaki try to escape from the hospital and they encounter mysterious cases one at a time.