Months have passed since Belle first met Gregor the Overlander, and her life has since been uneventful. But she and Gregor are destined to be key players in another prophecy, this one about an ominous white rat called the Bane. The Underlanders know that there's only one way that Gregor will come back: if they kidnap his little sister, Boots. The quest reunites Gregor with Belle, Luxa, and his new bond, Ares. They descend into the deadly Waterway in search of the Bane. If Belle and Gregor do not fulfill the prophecy, their lives, and the Underland, will never be the same.