"Author of the Printz Honor book Stolen"--Jacket.

Moss lives alone with her magician father and a dog on a magical island, until a tempest sweeps a wild, not-quite-human boy, Callan, onto its beaches, and the two grow close, despite her father's worries--and then one day, a young man from the outside world is shipwrecked on her island, and after that nothing will be the same again.