Cheng Yan was reincarnated and returned to the girls' dorm 407 twenty minutes before she was about to get attacked. She was sure that the 'random night dorm check' was a deadly trap, so ignoring her roommates’ doubts, she risked everything to block the door. The four of them teamed up to fight off the criminal pretending to be a dorm supervisor and eventually exposed the mole leaking student information. The case was solved, all four girls graduated safely, not a single one lost in 407, and then all these things happened.
