A beautiful love story in 1400's middle age Spain about the romance between the ones how would later get married and become Elizabeth, Queen of Castille and Ferdinand, King of Aragon. As a couple, the "Catholic Kings" who finally united the kingdoms into one that became known as Spain. The struggles and adventures of Ferdinand to penetrate into Castille territory to meet his cousin Elizabeth with whom he falls in love. How he saves her from her enemies who try to take away the throne of Castille from Elizabeth. How Ferdinand wins battles against the Castilean enemies using his magic sword "the black sword".