For as long as Lottie can remember, the only people who seem to care about her have been her best friend, Eliot, and the mysterious letter-writer who sends her birthday gifts. But now strange things and people are arriving on the island Lottie calls home, and Eliot's getting sicker, with a disease the doctors have given up trying to cure. Lottie doesn't know what she can possibly do—until a door opens in the apple tree. Down through the roots is another world—a world of treacherous, beautiful, impossible magic that just might lead to a cure for Eliot.