Thirteen year old Simon is growing curious as to why children are suddenly growing ill all around his peaceful village and wonders why the adults were keeping it a secret. Once his class had been full of classmates and now only he and three others remained. A shy and chubby boy named Rupert, the tall and cynical Caleb, an outspoken and animated girl named Sybille and Penelope, the smartest girl in class who happened to be Simon's best friend.
Stories of a beast visiting children in the middle of the night cause the kids to decide to solve this mystery once and for all even if it sounded ludicrous. They would hide inside his Rupert's closet that evening and wait for this beast to make his appearance and capture him! When they do they find out about a forgotten world that is beyond all their wildest dreams...