Thirteenth century. The reconquest is booming. A plague of locusts ravaged Castile and a woman in labor pain, stops her horse in the inhospitable wastelands of Toledo. Before giving birth, she does something strange: buries the baby's socks-and with them the secrets they contain. The woman is Beatrice of Swabia and the child who comes into the world is the future Alfonso X the Wise. Beatrice is next to her mother in law, Berengaria the Great, the most influential woman will have on the future king, for which planning a glorious destiny: to be the Castilian king to become Holy Roman Emperor. Years later, when Princess Kristina of Norway comes to Castile to marry Alfonso, she shall have the socks, but how is it possible? And above all, what mystery contain them?