In this book, Gregor is tricked into going back down to the underland by Ripred, who says that he will only be needed for a single meeting regarding saving the underland from a deadly paluge, when his mother doesn't let Gregor go, overland rats attack the family's apartment and eventually Grace lets Gregor go, as long as she can go with him. when they are down there, it turns out Ripred has lied to Gregor about it only being for one meeting, it also yurns out that Ares, Howard and Mareth's Flier: Andromeda, have contracted the plauge.