The stolen child : a novel
(Book)

Henry Day is seven years old when he's kidnapped from the forest near his home, The perpetrators? Changelings -- ageless beings whose community is threatened by modern life. Now Henry Day is Aniday, and he has the dubious gift of agelessness. In keeping with tradition, a changeling has been left in Henry's place, and he must adjust to a new way of life while hiding his true identity from the Day family -- though it's impossible for him to hide his talent for the piano. As time passes, the new Henry Day is haunted by memories of a German piano teacher and his prodigy. Now both Henry Day and Aniday search for who they once were.