In this exciting sequel to Gregor the Overlander , eleven-year-old Gregor finds himself headed back to the Underland, a huge territory beneath the earth that is populated by all manner of giant animals who have adapted over the years to living in perpetual darkness. The first time, he went to rescue his father, and he vowed never to return after surviving and succeeding on his quest. But now he must rescue his sister Boots, who has been kidnapped as a way to lure him back to the Underland. The Underlanders believe he is the one who has been prophesied to kill The White Rat and prevent an Underland world war. Gregor is again thrust into the role of reluctant hero. Scenes featuring amped-up species such as bats and roaches range from fast to funny to deliciously frightening. Gregor also faces several moral choices. As in the first volume of The Underland Chronicles , there is plenty of humor and plenty of intense action in this riveting, fast-paced novel. (Ages 9–14)

Spies have reported the sighting of a Rat King in the Underland, a character who has been legendary since the Middle Ages. Recognizable by its tremendous size and snow-white coat, the Rat King is destined to bring a World War to the Underland.