Kids all over the country are acting strangely after reading the latest books in the mega-popular Chillers series. First, it's the seemingly innocent Jelly Worm fad. But it quickly turns sinister, with exploding headaches sweeping the nation, and then a serpent surprise that lands several kids, including Franny's little sister, in the hospital.

Franny is convinced that I. M. Fine, author of the Chillers books, is behind it. With the help of her friend Beamer, she is determined to track down the mysterious author and find out once and for all if the books really are causing all the trouble. After all, a book can't be that dangerous, can it?