The evil wizard Mordack, brother of Manannan, shrinks Daventry's castle and its inhabitants and imprisons them in a bottle. Mordack threatens to feed the royal family to Manannan, transformed into a cat during the events of KQIII, unless Prince Alexander can restore him to his human form. King Graham, out for a walk when Mordack shrank the castle, is the only one unaffected by the spell. With the help of the wizard Crispin and his familiar, Cedric the owl, Graham travels to Mordack's castle to free his family.