After working overtime, ordinary programmer Chen Mo wakes up trapped in a strange classroom covered in mold. There is no way out, only a back door that opens at regular intervals. Every time it opens, it leads to a terrifying, potentially fatal scenario: a stitched-up monster in a midnight hospital ward, a cursed clown in an abandoned amusement park, a vengeful ghost in a haunted school... The scenarios are crawling with danger, and desperation twists human nature as betrayal and cooperation go hand in hand. Armed with a notebook left behind by someone who came before and a mysterious silver knife, Chen Mo fights to survive alongside his new companions, Zhao Qiang and Li Na. They must battle bloodthirsty monsters, compete for limited supplies, and search for scattered key fragments hidden throughout the scenarios. Every successful escape is a stroke of luck, and every time the door opens is a gamble. Only by staying alive will they have a chance to uncover the secrets of the infinite classroom and find the door to the outside world.
