The Fortress of Glass is the first in the Crown of the Isles trilogy, which will conclude the epic Lord of the Isles series. A true trilogy, the action extends over the whole three-book arc. The Fortress of Glass begins the story of how the new kingdom of the Isles is finally brought into being by the group of heroes and heroines who have been central to all the books in the series. The group includes Prince Garric, heir to the throne of the Isles; his consort Liane; his sister, Sharina; her herculean sweetheart, Cashel; his sister, Ilna, with her adopted child Merota; and piratical Chalcus. On giant triremes filled with soldiers and diplomats, they journey to the small kingdoms of the Isles to confirm the succession of Garric and to subdue, if necessary, any local rulers too fond of their own kingship to pledge fealty to Garric.

All this is being done in a time when the powers of magic in the Isles have flooded to a thousand-year peak, and even local magicians can perform powerful spells normally beyond their control. Fantastic forces from all angles try to keep them apart and unable to continue the reunification of the Isles. So, separately and together, they must fight their way back to the same time and place to combat the mysterious and supernatural menace of The Green Woman in her Fortress of Glass.