His father dead, his sisters kidnapped, a boy with an intuition for horses flees his home and is taken in by a veterinarian during the turbulent years of the Reconquest of medieval Spain  At the border of the Christian kingdom of Castile and the Muslim caliphate of Al-Andalus, a little inn sits on the front lines of the battle for Iberia. When word travels that the most feared fighters of the Muslim world, the Imesebelen, are advancing on Toledo, the innkeeper tells his son, Diego, to flee with his sisters. But Diego refuses to abandon his father. The old man and one of his daughters are slaughtered, and the other two girls are kidnapped. Now there’s only one thought on Diego’s mind: revenge. On his lightning-fast Arabian mare, Diego makes his way to Toledo. It is the start of a journey that will usher him into manhood and lead him to the dawn of a field of medicine that will change Spain—and the world—forever.