King Arthur is excited to see his old friends again and quickly arranges a wedding for King Pellinore. No trouble is spared—there are flowers, bells, and feasts. Meanwhile, far away Merlyn jumps up in bed—he suddenly remembers what he had forgotten to tell Arthur: his mother's name! Arthur's mother was Igraine—the very Igraine the Orkney brothers had spoken of who King Uther had captured.
Merlyn, although he knows already what will happen, is even himself caught by fate—he forgets to tell Arthur the one thing that might prevent his downfall, which would stop Morgause from being able to seduce him. This is where White's notion of fate becomes convoluted and thus a satire of itself: surely if Merlyn can see all, he knows that he will forget and could have prevented his forgetfulness.
Later that night after the festivities, King Arthur is sitting in the Great Hall alone. It has been a tiring few months, but finally it seems as if there might be peace. He thinks about being married one day to a beautiful woman and falls asleep. He wakes to find a beauty in front of him, wearing a crown. The spansel has worked its magic and Morgause seduces Arthur. Nine months later, Queen Morgause will have a baby boy by her half-brother Arthur called Mordred: Mordred will be King Arthur's downfall. Arthur does not know that he has slept with his half-sister and this is the tragedy of his demise—innocence aids his downfall.
This is the moment of Arthur's downfall and that which will destroy his Order of Knights. White very consciously informs us that this will be his downfall and by doing so forces the reader to see Arthur as an innocently, tragic figure—simple, yet ensnared by those around him.