There was a sudden power outage in the classroom for evening self-study. The students in Class 7 of Senior High School panicked when they discovered a line of blood written on the blackboard: "Tonight, one of you will die." No one knew who wrote it until the first victim actually appeared. Su Yuan and his classmates were trapped on campus and discovered that the killing was related to a forgotten tragedy three years ago. They must find the murderer before dawn, otherwise everyone will become a blood sacrifice.
