Nurse Moe Tachibana transfers to a new hospital, only to discover a strange rule: "Never enter the operating room after midnight." One night during her shift, overcome by curiosity, she disobeys and opens the forbidden door. Inside, she finds a sinister atmosphere and doctors conducting illegal human drug experiments. Caught breaking the rule, Moe is seized by the doctors and becomes their next victim. Her gentle smile will never be seen in this hospital again.