The knight rapes a maiden he sees walking home from the stream one day.
As punishment, the queen sentences him to death unless he can answer the question of what women most desire.
The knight sets out on a quest to find the answer to this question, but is unsuccessful.
The knight meets the loathly lady in a field when he is on his way back to Arthur's court, and promises to grant her request if she tells him what women most desire.
The knight successfully answers the question of what women most desire, but must marry the loathly lady when it turns out that's her request
Reluctantly, the knight marries the loathly lady, but refuses to sleep with her on their wedding night, telling her she's old, ugly, and lowborn.
After the knight listens to his wife's speech about the origins of gentility and the virtues of poverty, ugliness, and old age, he must decide whether to have his wife ugly but faithful, or young and beautiful with no guarantee of her fidelity.
The knight decides to turn the decision-making over to his wife, who rewards him for yielding sovereignty by becoming young, beautiful, and faithful.