Bridle the Wind — Joan Aiken

A JOURNEY GUIDED BY FATE
Shipwrecked, knocked unconscious, and imprisoned! To some this may seem like a streak of mighty bad luck, but Felix Brooke can't help but believe there is a reason for all his suffering.

When Felix finds an injured boy on the grounds of the remote monastery where he is being held captive, it seems his premonition may be right. Felix rescues the strange boy, Juan, from certain death, and together they escape the monastery and head for Spain. In their hazardous journey across the Pyrenees, Felix and Juan share many adventures. But there is a shadow over their happy times: Someone -- or something -- utterly terrifying is following their every move. Will they escape the evil that pursues them?