The evil Shadow Lord has become aware that Lief, Barda and Jasmine are searching for the seven lost gems of the magic Belt of Deltora. He knows that if the gems can be restored to the Belt its power will threaten his tyranny. Five gems have already been found. The next stone lies hidden in the underwater lair of the hideous and ferocious Glus. Already exhausted, and pursued by the servants of the Shadow Lord, the three companions will need all their strength and courage to face the Maze of the Beast.