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A year and a half after Alys, Charles, Janie, and Claudia complete their quest to the Wildworld, an earthquake hits California, potentially destabilizing the passage between the mortal world and the magical one. But with their parents overseas and the sorceress Morgana searching for the epicenter of the quake, the four children are on their own. Strange happenings in their town force them on a journey that will test their combined resources, for Thia Pendriel, Morgana’s archrival, has stolen a powerful gem—the Heart of Valor—and is waiting to spring her trap....