In Deep Dark Wood - Marita Conlon-McKenna

The mysterious arrival of Bella Blackwell, 'The Bird Woman', to the village of Ballyglen disturbs the peace and quiet of the Murphy household next door. Granny Rose is suspicious of Bella, and Rory doesn't trust her, but ten-year-old Mia falls under the old woman's spell. Bella tells Mia of a faraway place, a world where dragons and giants and ancient magic still exists, and asks Mia to become her apprentice and learn the old ways. One dark night Mia disappears and Rory, determined to find his sister, follows her to a world he does not believe in. Riding the 'Shadow Hound', he journeys to a strange land of legendary creatures and terrible dangers. Bella uses all her powers to prevent the brother and sister finding each other, but Rory begins a brave quest to rescue his sister, break the strange enchantment that Bella has over her and find a way home.