Landing with Sobrino upon a little isle, he found there King Sericane, who advised him to challenge the Christians to single combat in order to decide the outcome of the war, he, Gradasso, and Sobrino to stand in the lists against three Christian champions. Orlando agreed to do so, and selected for his companions in the fight Brandimart and Olivier. But the pagans were no match for Orlando, whom no weapon could injure, and Agramant and Gradasso soon fell, while Sobrino was wounded. But the joy over the Christian victory was not unalloyed by sorrow, for Olivier was severely wounded and the beloved Brandimart was slain.
The champions were now joined by Rinaldo, who after the breaking of the pact by Agramant, had set off for India in search of Angelica, whom he still madly loved. But Disdain guided his steps to the Fountain of Hate, one draught of which changed his love to loathing, so that he abandoned his undertaking and hastened to join the Christian forces in Africa.
Olivier's wound proved slow to heal, and when at last the warriors heard of a hermit on a lonely isle who could help him, they hastened to take their wounded comrade thither. There they found Rogero, who had been shipwrecked while sailing to Africa, and had been baptized by the hermit, who was warned in a dream of his coming. The Christian warriors gladly welcomed Rogero to their ranks, for they knew of his valor; and Rinaldo, who had learned how the young hero had saved the life of Richardetto and had preserved Vivian and Malagigi, embraced him, and at the suggestion of the hermit, plighted him to his sister. Before they left the isle, Sobrino was converted by the pious hermit, and Olivier's wound was healed.
The knights were received with the greatest honor by Charlemagne, especially Rogero, the new convert. But what unhappiness awaited him! In his absence Bradamant's father had promised the maid to Leo, the son of the Greek emperor, Constantine, in spite of her prayers and entreaties.
Although Bradamant declared that she would die sooner than wed another, the heart-broken Rogero hastily departed for Constantinople to slay his rival. In his absence, Bradamant besought Charlemagne not to compel her to marry Leo unless he could defeat her in single combat; and her angry parents, on learning of this, took her from the court and shut her up in the tower of Rocca Forte. Rogero, in the mean time, reached Leo's realms just as the Greeks engaged in battle with the Bulgarians. Because of his hatred for Leo, he fought with the Bulgarians, and when their king fell he rallied their scattered troops and put the Greeks to flight. Rogero then followed the fleeing Greeks unaccompanied, and being recognized, was taken captive that night as he slept in a hostelry. At the entreaty of a kinswoman whose son Rogero had slain that day, the emperor surrendered his captive to her, and he was thrust into a gloomy dungeon, where he suffered agonies from hunger and cold. But Leo, who had admired his valor in battle and had longed to know him, rescued him, recovered his horse and armor, and by his generosity compelled Rogero to admire him as much as he had before hated him. The news of Charlemagne's decree now reached Leo, and he, fearing to fight Bradamant, asked the unknown knight of the unicorn to take his place. Rogero's heart sank within him, but he dared not refuse. His life was Leo's, and he must sacrifice himself for him, must either slay Bradamant, or be slain by her for his deliverer's sake. He accompanied Leo to France, and feigning a cheerfulness he did not feel, changed armor and steed that he might not be known, and, while Leo remained in his tent outside the city, entered the lists and encountered Bradamant, who was determined to slay her hated suitor. Rogero was equally determined not to slay her nor to allow himself to be conquered. When twilight fell and king and court saw that while the young knight had not overcome the maid, he had not allowed himself to be overcome, they declared that the couple were well matched and that they should wed.
The hopeless Rogero hastened back to Leo's camp, changed armor and steed, and during the night stole away from the hateful place to the greenwood that he might die there, since he could never possess his beloved. At the same time, Bradamant gave way to her grief in such a manner that Marphisa, already indignant at the treatment of her brother, appeared before the king in his behalf. She declared that Rogero and Bradamant had already exchanged all the vows of those who marry and therefore she was not free to wed another. She then suggested that since the matter had gone so far, Leo and Rogero should meet in the lists to decide to whom the lady belonged.
Leo at once set out in search of his knight of the unicorn, who he believed would defend him from all peril, and found him in the forest, almost fainting from fasting and sleeplessness. The Greek embraced Rogero tenderly and implored him to betray the cause of his grief, and so tender were his words and so gracious his manner that Rogero could not but unbosom himself. And when Leo learned that his unknown champion was no other than Rogero himself he declared that he would gladly forego Bradamant for him, and would rather have forfeited his life than caused such grief to such a faithful friend.
Joy filled the court when the story of Rogero's fidelity was made known, and the joy was increased when ambassadors came from Bulgaria, seeking the unknown knight of the unicorn that they might offer their throne to him. Duke Aymon and his wife were reconciled when they found that Rogero was to be a king, and the wedding was celebrated with the greatest splendor, Charlemagne providing for Bradamant as though she were his daughter.
In the midst of the celebrations Rodomont appeared to defy Rogero, and that knight, nothing loath, met him in the lists. The Moor fell under Rogero's blows, and all the Christian court rejoiced to see the last of the pagan knights fall by the hand of their champion.