Twelve-year-old Zackary is the seventh son of the King and Queen of Solaris, and a most reluctant knight. In despair, the King and Queen assign him to the castle administrator, Barnabas, who sends him on an errand to the Zoo of Magical and Mythological Creatures. Mistaken for a job applicant, Zackary starts working at the zoo with the resident sorcerer, Acacia. Powerful magic is needed to control some of the extraordinary creatures in the zoo: from the Stymphalian birds of Greek mythology and the nine-headed hydra, to manticores from India and the squonks - Drufflefuster, Gobblesnocks, Snivelsnork and Grimelgrout. But just as Zackary is settling in to his double life, a shadow is cast across the entire kingdom with the news that a strange creature is expected at the zoo - a creature which spreads evil and destruction in its path.