Earthquake damage leaves Winding Circle vulnerable to pirate attack, so everyone - including the young mages-in-training Tris, Briar, Daja, and Sandry - is working to strengthen the community's defenses. When Tris's cousin Aymery comes to visit, he advises the "weather witch" to return to the family that exiled her, but she doesn't wish to leave her friends to face the threat without her.

As the onslaught begins, two things become terribly clear: The pirates have a powerful new weapon, and they have an accomplice within Winding Circle. But the attackers have failed to reckon with the fury of a young mage betrayed once too often and her very stubborn, very loyal friends.