1. On the first day of school, Shen Zhao approached Song Zhixia and invited her to join the biology club, but his pupils suddenly shrank when he touched her mask.
2. Song Zhixia discovered that Shen Zhao disappeared on time at 17:00 every day, and followed him to the abandoned laboratory building to hear him talking to the professor: "Sample A07 started to reject the reaction."
3. Key conflict: Song Zhixia discovered that Shen Zhao was injecting medicine into himself in the laboratory, and he choked him and threatened: "If you don't want to die, just pretend not to know."
4. Reversal: The list of fire survivors shows that Shen Zhao and Song Zhixia should have died in the same accident, but he had no trace of burns.
