Eleven-year-old Gregor and his younger sister, Boots, return to the Underworld beneath New York City to find the cure for a terrible plague that threatens the life of their mother, as well as the lives of the people, bats and rats who populate the underworld.
Collins, Suzanne, 1964- Underland chronicles ; bk. 3.
Underland chronicles ; bk. 3
Brothers and sisters -- Juvenile fiction.
Fantasy -- Juvenile fiction.
Plague -- Juvenile fiction.