Senior college student Lin Jian is reborn back to December 12. On this night in her past life, three thugs tricked open the door of dorm 507, and none of the four female students staying on campus survived. She desperately blocked the door to stop them, but her roommate Zhou Yue insisted on opening it for fear it would affect her postgraduate recommendation. The female dorm inspector outside reported the four names and late-night return records, before finally revealing a male voice and violently breaking the door down. The four desperately braced the door and called the police, waiting for the police and security office until everyone survived.