The Underland Chronicles Book Four: Gregor and the Marks of Secret

From School Library Journal Grade 5-8–No good deed goes unpunished in the fourth installment in the popular series. Gregor and his sister Boots are regular visitors to Underland, where their mother is slowly recovering from injuries incurred in the previous episode. Gregor is supposed to be studying echolocation with his rat friend, Ripred the Gnawer, but hes doing very badly. Ripred has his own problems, largest of which is Bane, the once-sweet little baby Gnawer whom the protagonist refused to kill in