The day before Kay is to be knighted, Pellinore arrives at Sir Ector's and informs him that the King, Uther Pendragon, has died without an heir. He also explains that, in London, a sword has mysteriously appeared that passes through an anvil (a heavy blacksmith's block on which he bangs pieces of metal) and then into a stone. The inscription on the pommel reads, "Whoso Pulleth Out This Sword of this Stone and Anvil, is Rightwise King Born of All England." On New Year's Day, Pellinore explains that a tournament will be held so that all the men of England can try to remove the sword. Kay asks his father if they may visit the capital for the tournament, and Sir Ector eventually agrees. The Wart, unaware of the events in London and brokenhearted at Merlyn's announcement that he is leaving, then enters with his tutor.
Sir Ector and his boys travel to London for the tournament. When Kay arrives at the tilting grounds, he realizes he has forgotten his sword and sends the Wart (now his squire) back to their inn to retrieve it. Finding the inn locked and no one inside, the Wart desperately searches for a replacement sword. He approaches the sword in the stone (having no idea of its significance) and, after a struggle, removes it. (All of his animal friends watch and coach him as he makes his attempts.) When he brings it to Kay and tells of how he got it, Kay lies to his father and says that he (Kay) pulled it out of the stone. Kay eventually confesses that the Wart pulled it out. Ector and Kay then fall to their knees and hail the Wart as their new King. The Wart, confused and embarrassed, bursts into tears.
The novel ends with the Wart's coronation and a party that is thrown after it. All of the characters attend the party and bring the Wart a number of gifts. The last gift is given by Ector: a cone that looks like a dunce cap that is lit at one end, which turns into Merlyn. The magician explains that Uther Pendragon was the Wart's father; Merlyn knew this, of course, but was forbidden to mention it to the boy. Merlyn then asks the privilege of being the first of the Wart's subjects to address him with his new tittle: King Arthur. Merlyn also reassures his new King that he will stay with him for a long time.
