When sixth grader Jeremy Chase meets a strange visitor who wants to transport him to the mysterious land of Teradawn, Jeremy thinks nothing of it. Then his younger sister Sandy is mistakenly taken instead. Jeremy and Priscilla, Sandy's twin, find a way to Teradawn where they are desperate to rescue their sister and return home. In Teradawn, those who claim to be their friends seem less and less friendly. Their enemies continue to grow in number, and their only hope for rescuing Sandy is to master the elusive power of the Language. Meanwhile, they must grapple with the most pressing question of all: who has kidnapped Sandy, and why?