On the way home from school, Violet discovers A. quaestio, the gigantic underground mushroom, has broken through the center of town and is engulfing the town square and destroying the Mayor’s beloved fountain. Later that day, while doing homework in her room, Violet notices a flash of purple light. Going outside to investigate the next day, she puts on a mask and discovers the fungus has released a strange wave of spores from the center of town and that most of the townspeople including Violet’s father, Iris, Bruno Ellis, Ms. Holly Peterson, Ms. Twombley, and baby Freddie, are now all unconscious.
Violet locates Officer Ron, who has been out of town looking into allegations surrounding the mysterious CM Waldorf. Together they find Mayor Zisk in tears at her ruined fountain. Violet hurries to the library and discovers a similar incident happened before in Question Mark in 1993 after a poisonous explosion at an illegal pyrite mine owned by Thompson Zisk. Violet heads alone to the mine and locates several crates of hazardous materials and then receives a message from Quentin Quinn, warning her that history is repeating itself and the answer may lie at the Cell-Con plant, the cell phone factory formerly owned by Thompson Zisk.
At the abandoned factory, Violet and Officer Ron find an old safe containing several documents that reveal a second incident occurred in 1998 after a chemical spill at the Cell-Con plant, leading to several dozen people becoming immobile. Decoding a private letter to Mayor Elizabeth Zisk, Violet also learns that Thompson Zisk claimed to have buried hazardous waste somewhere in town and may have also burned down his own factory in order to destroy evidence and sever ties with his failing business.
Following these clues to the town dump, Violet and Officer Ron make another unbelievable discovery that may explain strange symptoms currently affecting town members, but will this discovery come too late?