Now Alfonso was greatly troubled when he knew that Bernaldo was aware of his lineage and of his father's imprisonment, but his hatred for the man who had won his sister was greater than his love for his nephew. At first he made no reply, but sat plucking at his beard, so taken aback was he. But kings are not often at a loss, and Alfonso, thinking to brush the matter aside by brusque words, frowned, and said sternly: "Bernaldo, as you love me, speak no more of this matter. I swear to you that never in all the days of my life shall your father leave his prison." "Sire," replied Bernaldo, "you are my king and may do whatsoever you shall hold for good, but I pray God that He will change your heart in this matter." King Alfonso had no son of his own, and in an ill moment proposed that Charlemagne, the mighty Emperor of the Franks, should be regarded as his successor. But his nobles remonstrated against his choice, and refused to receive a Frank as heir to the throne of Christian Spain. Charlemagne, learning of Alfonso's proposal, prepared to invade Spain on the pretext of expelling the Moors, but Alfonso, repenting of his intention to leave the crown to a foreigner, rallied his forces around him and allied himself with the Saracens. A battle, fierce and sustained, took place in the Pass of Roncesvalles, in which the Franks were signally defeated, chiefly by the address of Bernaldo, who slew the famous champion Roland with his own hand. These and the other services of Bernaldo King Alfonso endeavoured to reward. But neither gift nor guerdon would young Bernaldo receive at his hands, save only the freedom of his father. Again and again did the King promise to fulfil his request, but as often found an excuse for breaking his word, until at last Bernaldo, in bitter disappointment, renounced his allegiance and declared war against his treacherous uncle. The King, in dread of his nephew's popularity and warlike ability, at last had recourse to a stratagem of the most dastardly kind. He assured Bernaldo of his father's release if he would agree to the surrender of the great castle of Carpio. The young champion immediately gave up its keys in person, and eagerly requested that his father might at once be restored to him. The treacherous Alfonso in answer pointed to a group of horsemen who approached at a gallop. "Yonder, Bernaldo, is thy father," he said mockingly. "Go and embrace him."