Dorm inspection tonight—don't open the door!!

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.