Long ago, Milon Redshield, the first warrior-king of Windkeep Castle, brought down a curse on the kingdom for his cruel treatment of dragons, the Goddess Nilene's chosen guardians of nature. Thousands of years later, Windkeep is still burdened with the curse, and Queen Tessia is having to defend her kingdom from repeated assaults by the weather witches and their allies. She turns to her friends and advisors Norbert the Green Mage and Tyrmiss the Last Dragon, to accompany her and a band of heroes in a quest to travel to the far land of Sheonad in order to parley with the witches, and if they refuse to negotiate, then to destroy their city. Tessia urges Norbert to use his powers to fight the witches and protect Windkeep, but Norbert is reluctant to do so because he understands that the world exists in delicate balance, and grave and unforeseen consequences result if the balance is disrupted. After fighting a number of battles and suffering bizarre magical transformations, Tessia and Norbert at last come to understand the kingdom of Windkeep can be saved only through the ancient wisdom of dragons.

Windkeep is book two in a YA fantasy series about Tessia the Dragon Queen and her loyal advisor and friend Norbert Oldfoot, a gentle mage who has no desire to wield the powerful magics he probably could use if he were not such a good person. Norbert is the self-deprecating narrator of the story, as he was for book 1, The Green Mage.

Windkeep opens with a bored Queen Tessia seven years after the events of book 1. The kingdom is suffering a devastating drought, and when a traveler comes to town, he tells tales of the kingdoms and peoples to the north, including weather witches, who could bring rain, Tessia and her ministers believe him.

Tessia, Tyrmiss the dragon, and Norbert set off with a few others to set the kingdom to rights through diplomacy, and it all goes terribly wrong when they run afoul of a magic that turns all but Norbert into magically mismatched creatures. Can Norbert return his friends to their own shapes? And beyond that, will he and his magically transformed friends be able to save the kingdom?