The chapter recounts the origins of Sir Dagonet, a melancholy juggler from the Fenlands who joined a minstrel troupe and arrived at Camelot with a clever pickpocket-and-juggling act involving Arthur's signet ring. Charmed, Arthur knighted him as a fool-knight, granting him full honors. Dagonet privately suffered nameless dread and depressions, finding solace only in juggling, which felt to him a glimpse of cosmic order beneath a meaningless world.

In the twenty-third year of Arthur's reign, on Whitsunday, a marble block bearing a sword floated down the river Brass. The inscription declared it could be drawn only by the world's best knight. Lancelot refused to attempt it, sensing it was not for him. Gawain tried and failed; Lancelot warned him the sword would one day wound him badly. Percival, Bors, Gareth, Palomides and others also failed.

During lunch, a beautiful boy in white samite, escorted by an aged monk, entered the hall and sat in the Siege Perilous, the cursed empty chair. Golden letters spelled SIR GALAHAD. Galahad then claimed the floating sword effortlessly. A tournament followed, after which the Holy Grail itself appeared in the hall, healing wounds and granting each knight his desire. Dagonet felt unprecedented peace, but noticed Galahad alone seemed unmoved.

Every knight mobilized for the Grail Quest, except Arthur, who declined citing age and duty. Rumors spread that the true prize was succession: with no legitimate heir, whoever found the Grail would inherit Britain's throne. The unassuming Sir Constantine of Cornwall insisted on partnering with Dagonet despite Dagonet's protests. They set out late, and on the fourth day reached Sir Turquine's castle Blackfast. Constantine sounded the challenge basin; Turquine emerged and unhorsed Constantine, injuring his knee. Dagonet surrendered without fighting.