After a vicious storm aboard ship, fourteen-year-old Caleb is tossed into the Atlantic Ocean. Frightened and alone, he finds himself nudged awake. He's been recovered by one of Sable Island's legendary wild stallions and is given shelter by a mysterious stranger, Norse, who is secretly living on the island. As Caleb recovers and gets to know his strange rescuer, learning the art of scrimshaw, storytelling, and survival, he wonders how he'll manage to remain on the island he's come to love. When he befriends the ghostly girl who rides bareback over the dunes, he knows he must do whatever he can to save her, and himself.