The Witches of Eileanan (The Witches of Eileanan, #1)

In the Celtic land of Eileanan, witches and magic have been outlawed, and those caught for practicing witchcraft are put to death! It is a land ruled by an evil Queen, where sea-dwelling Fairgean stir, and children vanish in the night. But in a valley deep in the mountains, young Isabeau grows to womanhood under the guidance of an elderly witch, and must set out on a quest, carrying the last hopes of the persecuted witches.