Meanwhile, Sir Mordred has been up to some shady business back on the home front. He has produced false letters claiming that Arthur is dead, and has declared himself the King of England. Sneaky sneaky.
Mordred also tries to marry Gwenyvere, but she locks herself in the Tower of London. He's that gross.
The Archbishop of Canterbury excommunicates Mordred for trying to marry his father's wife, and then withdraws to Glastonbury Abbey when Mordred tries to kill him.
When Arthur receives word of Mordred's treachery, he sails to England, forcing Mordred's troops into retreat at Dover.
In the battle, the wound Gawain received at Launcelot's hands worsens, causing him to take to his deathbed.
Before his death, Gawain writes a letter of reconciliation to Launcelot, asking him to pray at his tomb, and to come to Arthur's aid.
Arthur manages to force Mordred's army back to Salisbury Plain, where the two parties agree to do battle on the Monday after Trinity Sunday.
The night before the battle, Arthur dreams that he's tied to a wheel that plunges into black water full of serpents and horrible beasts. That doesn't sound like a very good sign.
What's worse, he also dreams that Sir Gawain tells him that he will die the next day if he does battle with Mordred.
Because of this vision, Arthur's knights advise him to make peace with Mordred and cede some lands to him, so he can, you know, stay alive.
Mordred agrees to this, but during the signing of the treaty, the presence of a black snake causes one of Mordred's men to draw his sword, leading all the knights to begin to fight.
Arthur kills Mordred by running him through with a spear but, before he sinks to the ground, Mordred plunges his own sword into Arthur's head. Ouch. That's gonna leave a mark.
Aware that he has received his death-wound, Arthur tells Bedivere to throw his sword into a nearby lake. Bedivere hesitates at first, but upon his third attempt manages to throw the sword in, upon which he sees a hand rise from the lake and catch it.
When Arthur hears this, he tells Bedivere to take him to the lakeside. There, a barge bearing three ladies takes Arthur's body to Avylyon where, Arthur says, he will either be healed of his wounds, or die.
Bedivere comes to the chapel where the Archbishop of Canterbury has withdrawn, and there, finds Arthur's body. He decides to become a hermit there.
The narrator tells us that Arthur was taken away on the barge by his two aunts Morgan le Fay and the Queen of North Gales, along with the Queen of the Waste Lands and Dame Nyneyve.
He also tells us that some people believe that Arthur did not die, but only went to another place from which he will return to complete the Crusades.
People also say that written upon his tomb is "Hic iacet Arthurus, rex quondam rexque futurus" – "Here lies Arthur, king who was, and king who will be."
When Gwenyvere learns of Arthur's death, she withdraws to Amesbury and becomes a nun.
When Launcelot receives Gawain's letter of reconciliation, he heads to Dover, where he prays at Gawain's tomb.
Then, he finds Gwenyvere at Amesbury, but she tells him that she has forsaken his company forever and become a nun in penance for the sin they two committed, which she believes caused the downfall of Arthur and his knights. Well, she kind of has a point.
Launcelot travels to the abbey where Bedivere resides and becomes a monk and priest there, too.
After six years, Launcelot has a vision telling him that Gwenyvere has died, and that he must fetch her body and bury it beside Arthur, which he does.
The sight of Arthur and Gwenyvere's bodies buried together causes Launcelot to refuse food and water, and he dies within six weeks.
The Archbishop of Canterbury has a vision of Launcelot being received in heaven at the moment of his death.
All of Launcelot's knights take holy orders, and become monks, too.
Sir Cador's son, Sir Constantyn, becomes King of England.
The narrator asks everyone who reads this book to pray for his soul, and declares his story at an end. And we Shmoopers collapse on the floor from exhaustion.