Joan Aiken 
Bridle The Wind [EPUB ebook] 

Packed-off to boarding school and bullied by his peers, Felix feels sad and trapped. Although he has a home in England, his heart lies in Spain – so he runs away. But Felix’s journey is cut short when his ship is caught in a storm off the French coast. Despite being shipwrecked and then held prisoner in a remote monastery, Felix’s spirit is far from broken – and he needs all the strength he can muster to battle against the demonic Abbot Vespasian and his evil powers . . .