Felix Brooke Series by Joan Aiken

Felix Brooke, the orphaned son of an English soldier and an aristocratic Spanish mother, has been raised in the strict, loveless household of his grandfather in Villaverde, Spain. When Felix gains possession of a letter that contains a clue to the whereabouts of his father’s family, he gladly runs away from home to pursue the trail. His journey from Spain to far-off England begins the adventure of a lifetime.

His journey back to Spain interrupted by shipwreck, loss of memory, and a stay in a forbidding French monastery, twelve-year-old Felix finally continues his journey in the company of a mysterious boy that he had rescued from hanging. Sequel to Go saddle the sea.

Now eighteen, Felix sets out across the mountains of Spain to rescue three children kidnapped by their father. Along the way, he hopes to see his true love, Juana, who has entered a convent. But his rescue party is being followed, and Felix fears he and the children are being led into a trap.