In these selections, the reader learns how the envy and hatred of the romance between Queen Guinevere and Sir Lancelot starts the fall of King Arthur and his court. Sir Agravain and Sir Mordred know of the love affair, and they tell King Arthur who has been ignoring the situation. The two knights devise a plan to catch Lancelot and Guinevere together; the king goes hunting, leaving the queen alone. Although Sir Bors tries to stop Lancelot, he goes to Guinevere and the lovers are caught.

Lancelot fights his way out of the Queen's chambers and flees from the court. However, in his escape, Lancelot kills eleven men, and two of the victims are Gawain's brothers. While Sir Gawain, the King and his loyal knights go to avenge these deaths in a foreign land, Sir Mordred betrays his father and takes over the kingdom. They are forced to return, so they can fight to regain control of the kingsom. Sir Gawain is killed in battle by Mordred's men.

Merlin's prophecy states that Arthur will die at Mordred's hands, so he sends Sir Gawain's spirit to warn Arthur to seek a temporary truce. Just before this meeting, both sides warn their men to make sure no swords are drawn. War breaks out after a soldier thoughtlessly draws his sword to kill a snake. King Arthur is fatally injured.

King Arthur's dying request is for Sir Bedivere to throw the Excalibur into the lake, but Bedivere's greed temporarily prevails over his loyalty. He lies twice to Arthur about throwing the sword back. On his third trip to the water, he fulfills Arthur's dying wish. Sir Bedivere brings King Arthur to the magical barge that will take him to Avalon.

Queen Guinevere then becomes a nun at Amesbury, asking, just before she dies, to be buried next to King Arthur. Lancelot, who has become a priest, dreams of Guinevere's death three times, arriving just after she dies. He performs the funeral mass and makes sure her request is fulfilled. Struck by guilt, Lancelot tries to atone for his sins by starving himself to death.