Oliver has settled into his life as the 113th assistant librarian. He loves his job - even though it sometimes includes battling giant crabs or fending off firedrakes - and his new friend, the mostly-human Agatha, is always on hand to help.

But when he discovers a rare edition of a history book with unique wording, he realises the slightest misinterpretation could endanger the entire kingdom. Determined to solve this mystery, he and Agatha leave the library - with the help of an unpredictable transporting book - to establish the truth. But can they prevent Annabel Clowritch, the esteemed Member for Upper-Lower Tumbledown Barrows, from using the text to her own advantage . . . and stop a war?