The defeated Lot returns home and the three English knights are shocked to learn that Orkney has been at war with England. Morgause heads south to England in order to reconcile with the English, and brings with her her sons and the three knights. Arthur conducts the wedding of Piggy and Pellinore, whom he remembers fondly as the first knight he ever met. At the same time, St Toirdelbach also marries. After the ceremony Morgause seduces Arthur and becomes pregnant. It is then that Merlyn, far away in North Humberland, remembers that he had forgotten to tell Arthur that Morgause was Arthur's half-sister, so Arthur's adultery is also incest. Morgause becomes pregnant with Mordred, who will one day come to ruin his father's kingdom.