From A High Tower - Mercedes Lackey - E-Bog

When a man is caught stealing from a walled garden owned by a strange woman, he bargains away his youngest daughter in return for food for his family. The woman, rumored to be a witch, takes the golden-haired child and locks her away in a high tower. Sixteen years later, Giselle has lived an isolated life, but her adoptive mother has trained her in Air magic, and Giselle must use her new skills on a quest to avenge her broken heart... ...