While in Germany with their father, who is researching the Pied Piper legend, Max, nearly thirteen, and her brother Carter, ten, are spirited away to the magical land where the stolen children of Hamelin have been hidden since the thirteenth century.

On the mysterious Summer Isle, siblings Max and Carter discovered the magical land where the villainous Pied Piper led the children of Hamelin centuries ago. They were trapped outside of time in a never-ending clash against a vicious rat army. After a desperate battle with a cruel soul-stealing magician, Max and Carter found themselves separated: Max with their newfound allies (human and trollson alike), Carter with . . . the Piper. -- amazon.com