Classroom 404 in Teaching Building No. 3 Of Qingyu University is an abandoned storage room during the day, but it "emerges" at night, involving certain freshmen in a death game - names and rules appear on the blackboard every Monday and Friday, and those who fail to complete the game die mysteriously.
Lin Ye, a freshman in the Department of Computer Science, unexpectedly joins the game and forms a team with the vicious foodie Su Xiaoyu and the cool-headed academic Xia Wanxing. They solve mysteries such as "Obsession Chalk" and "The Disappearance Case of 1998" while making jokes between life and death. Everyone relies on their special abilities (spiritual touch, death recall, etc.) To track down the mastermind behind the scenes. Lin Ye is also fighting side by side, firmly choosing Xia Wanxing among the three relationships.
The story interweaves scary rules, school history secrets and funny daily life, with hidden foreshadowing. In the end, obsession is resolved with "forgiveness", but the suspense of organizations outside the school remains to be solved.
