Aimed at core or guided reading stages, the books in this series help to build up stamina and increase vocabulary and language skills. Stories about familiar Oxford Reading Tree characters should encourage the children to read on. The same stories in different genres (narrative and play) help to consolidate vocabulary and demonstrate how a story can be presented in different forms. In this title, Chip, Wilf and Wilma are whisked away by the magic key to help decipher a treasure map on Mirror Island.