Gold-medal murder mystery game player Lin Ran enters the out-of-print loop script "Underground Library Mystery", becoming the cannon fodder Lin Ran destined to die in a bookshelf accident in seven days, binding with the deduction sprite Xiao An. She cracks multiple tricks, exposing campus academic fraud and school-enterprise dark secrets. The script has looped 126 times, resetting whenever the core is touched. Lin Ran meets Jiang Shixu, who retains his memories, and learns the world originates from the obsession of the original Lin Ran, who back then sought justice for Su Wanxing, got trapped in the consciousness-constructed script, and quietly awaited future generations to break the game. Lin Ran gathers all the truths to trace back ten years, stops the murder, and ends the loop. Returning to reality, she and Jiang Shixu reunite at a murder mystery game store.