Chen Mo was reincarnated and returned to the sophomore class of high school in 1998, only to find that he and his classmates were all "returnees" who had died violently in their previous lives. A blood-stained exercise book is engraved with five strange rules, declaring that "one person must 'go back' (die) within seven days." At the same time, the "Instructions for Admission" promulgated by the school library hides murderous intent. Black books, cries and warnings from "administrators" constitute a fatal trap.
Chen Mo formed an alliance with his deskmate Zhou Xiaoya, whose life experience was a mystery. While investigating the mysterious death of his classmates and the secrets of the library, he gradually uncovered the dusty past of human experiments at the Red Star Machinery Factory. They discovered that the head teacher Wang Xiulan was actually the leader of the experiment, treating the "returnees" as "samples" for manipulation, and that the key to breaking the cycle of death was buried behind a "door" deep in the library. In order to survive, the two must regain the key to rewrite their destiny in the game of strangulation and human nature with strange rules before the seven-day countdown ends.
