Every year, the people of the Protectorate leave a baby as an offering to the witch who lives in the forest. They hope this sacrifice will keep her from terrorizing their town. But the witch in the Forest, Xan, is kind and rescues the children and delivers them to welcoming families on the other side of the forest, nourishing the babies with starlight on the journey.

One year, Xan accidentally feeds a baby moonlight instead of starlight, filling the ordinary child with extraordinary magic. Xan decides she must raise this girl, whom she calls Luna, as her own. As Luna's thirteenth birthday approaches, her magic begins to emerge--with dangerous consequences.