During the feast of Pentecost, a tall, handsome young man appears at Arthur's court with a dwarf and two other men, and asks Arthur to grant his request, or "boon."
His request is that he be given food and lodging in Arthur's household for one year, plus two other requests to be made at a later time.
Because he doesn't ask for knightly things, everyone assumes the young man is low-born.
Kay, who taunts the young man mercilessly, nicknames him Beaumains, or "fair-hands," because of his beautiful hands that look like they've never done a day's work.
On the feast of Whitsuntide, a lady appears in court asking for the help of Arthur's knights to rescue her sister from the Red Knight, who has besieged her castle.
Beaumains asks for his final two boons: to be allowed to undertake this quest, and to be knighted by Sir Launcelot at a later date. Good ol' Arthur kindly grants his requests.
The lady is unhappy to be given only a "kitchen-boy" (rude, much?) to help her and tries to ride away without him, but he follows her anyway.
Kay rides after Beaumains to joust with him, pursued by Gawain and Launcelot.
Beaumains jousts with Kay and defeats him. Then he jousts with Launcelot. It's a tie, and Launcelot knights him. Beaumains then continues on his journey.
Beaumains rescues a knight from six thieves who have captured him. Then he defeats two knights who are guarding a river-crossing. Despite his past victories, the lady continues to taunt him, telling him his victories are only dumb luck. She's not the nicest traveling companion.
Then Beaumains kills the Black Knight, too, and then faces off with the Black Knight's brother, the Green Knight, and refuses to show him mercy unless the lady requests it, which she does, grudgingly.
Then Beaumains overcomes the Black and Green Knights' brother, the Red Knight. He's got those colors covered.
All but one, it turns out. Soon, Beaumains and the lady come to a beautiful plain before a great city, where the Blue Knight, Sir Persaunte of Inde, is on vacation.
The lady suddenly has a change of heart towards Beaumains, and begs him to save himself, warning him of the Blue Knight's prowess.
But Beaumains totally has more prowess, and defeats Sir Persaunt of Inde, who turns out to be another brother of the three knights he has previously defeated. He and the lady stay with Sir Persaunt that night.
Sir Persaunt sends his daughter to seduce Beaumains, but when he learns who she is he refuses her out of respect for his host. When Sir Persaunt learns this, he declares Beaumains must be nobility.
So Beaumains reveals his identity to Sir Persaunt and the lady (who, we have learned, is named Lyonet). He is Sir Gareth of Orkney, nephew to the king and brother of Sirs Gawain and Gaheris. Oh so that explains it.
Lyonet's sister learns of Sir Gareth's arrival and sends food and wine for him to a nearby hermitage.
Then, Gareth defeats the Red Knight (there's yet another one), breaking the siege around Lyonet's sister's castle.
Apparently the Red Knight laid siege to the castle in order to provoke Gawain and Launcelot, who killed the family members of a lady he loved. Or so he tells Gareth.
Gareth falls in love with the lady of the castle, Lyonesse, and she with him. She sends him away to adventure for a year's time, which doesn't strike us as all that loving, but hey, what do we know?
Lyonesse sends her brother, Sir Gryngamour, to capture Gareth's dwarf so she can learn Gareth's real identity. At the castle of Sir Gryngamour, the dwarf reveals Gareth's identity to Lyonesse, who is pleased by it (who wouldn't be?).
Sir Gareth arrives at Sir Gryngamour's castle in search of his dwarf, and is lodged there and seduced by Lyonesse in disguise.
Lyonesse reveals her true identity to Gareth and they become engaged. They make a plan to have sex. Lyonesse goes to Gareth's bed, but the lovers are interrupted again by a knight enchanted by Lyonet, who has discovered their plan. Irked by the interruption, Gareth cuts off that guy's head.
The Red, Green, and Blue Knights arrive at Arthur's court to pay homage. Arthur makes the Red Knight a member of the Round Table.
Lady Morgause (the mother of Gareth, Gawain, and Gaheris) arrives at Arthur's court demanding to know what has happened to her youngest son, Gareth.
When Arthur and the knights learn the true identity of "Beaumains," they are eager to find him, too, so they send for Dame Lyonesse.
When Lyonesse receives the message, she tells Gareth, who advises her to request that Arthur and his knights declare a tournament, to be held at her palace, with the winner receiving her hand in marriage. She does so. Our Gareth must be a pretty confident dude.
The Red and Blue knights agree to fight on Sir Gareth's side against Arthur's knights during the tournament.
Lyonesse gives Gareth a magic ring that makes him change colors. We're assuming this just might come in handy later.
Gareth does well during the tournament, but when his identity is discovered (because it's written on his helmet) he uses his magic ring to ride away in disguise.
On the run, he receives lodging in a castle in a forest in exchange for his promise to yield to the owner of the castle whenever he meets with him.
While out and about, Gareth defeats and escapes from the castle of Sir Bendelayne, he rescues the castle of thirty weeping widows from the Brown Knight, and he meets the Duke de la Rowse, at whose castle he had formerly lodged, and jousts with him, too. How's that for adventure?
Sir Gawain meets with Gareth and they joust until Lyonet arrives and tells him it's his brother. The two men embrace. Ah, brotherly love.
King Arthur and Lady Morgause arrive on the scene, and Arthur immediately gives Gareth and Lyonesse permission to marry, which they do, at Michaelmas (another Christian holiday).
Their other brother, Sir Agravain, marries a cousin of Lyonet and Lyonesse. Happy times.
Arthur makes the Green Knight and the Duke de la Rowse Knights of the Round Table. He and the Red, Green, and Blue knights all pledge their fealty to Gareth, the lucky guy.