Once the partying and charm offensive die down, everyone pretty much assumes that Sir Tristram and the lovely Isoud will be wed. Certainly it’s what Queen Isoud and King Anguish expect. But Tristram keeps failing to ask for her hand, and it starts to bother Anguish. A few weeks after their return to Ireland, he takes Tristram aside and asks what’s up.
“I figured you were going to use that boon I promised you to score my daughter’s hand. She likes you, you like her, I like you too, I don’t see the problem with that. It’s win-win-win. My wife still dislikes you on account of you killed her brother, but hey, her mother disliked me. No big! So what’s the holdup?”
“Well, see,” Tristram begins, and trails off. “There’s this…” he starts again, and trails off again.
“Spit it out, pal! We’re all friends here.”
“I promised my uncle King Mark of Cornwall that I’d fetch the lovely Isoud back to his court so he could marry her,” Tristram says all in a rush.
“So I beg you to grant me that boon as you promised, so I can keep my promise, and deliver your daughter to my uncle.”
“She’ll be married to him. He’s a king; it’s a good match.”
“….didn’t you and she exchange rings at the end of Chapter XII? Certain promises were made of a remaining-faithful-to-one-another nature. At least that’s what she told me.”
“Yeah,” Tristram looks pained. “There was this lady-in-waiting, Sally, and… really I haven’t been faithful to her? So I should at least be faithful to my uncle?”
Anguish grunts. “I really feel you’re springing this on me somewhat unfairly. But fine. Fine. You know your heart. I’ll give you my daughter, the lovely Isoud, and you can turn around and pass her right over to King Mark, if that’s what you want. Fine.”
So long story short, the lovely Isoud and her henchwoman Dame Bragwaine get on a boat with Tristram and Gouvernail and a load of sailors too (probably) to head back to Cornwall.
As they’re packing up, Queen Isoud (the lovely Isoud’s mother) pops in on Gouvernail and Bragwaine. She’s come with a gift for her daughter, to ensure a happy marriage: a magical love potion, two doses, one for the lovely Isoud to drink on the wedding night, and one for King Mark. Gouvernail and Bragwaine pack up the doses and everyone sets off.
Days go by, and one day Tristram and the lovely Isoud are in Tristram’s cabin, thirsty. Why they’re thirsty, why they’re alone in Tristram’s bedroom together, whether they’re making the most of this period before sleeping together would count as adultery instead of mere fornication, all of that Malory doesn’t go into. He skips to the part where they’re thirsty and going through their bags and they find what they think is a couple of pints of wine, in special bottles, secreted away.
“Look at that!” says Tristram. “My manservant and your henchwoman have hidden some really top-flight wine away in their baggage! It’s all marked with your mother’s seal and in a golden flask and so on.”
“Let’s be bad, and drink their wine!” suggests the lovely Isoud.
Which they do.
Sometime later, Tristram emerges from his cabin long enough to announce that the ship is no longer bound for Cornwall, but for someplace remote and safe where love is celebrated and people are free to marry whomever and blah blah blah. So the steersman turns the boat around and starts sailing aimlessly, and Tristram and Isoud loved each other so well that never their love departed for weal or woe. It may have been legitimized by a magic potion, Malory tells us, but their love never departed the days of their life.
Eventually the ship lands at Castle Weeping. Funny story about Castle Weeping: any ship that puts in there, if a knight and a lady are on board, they are taken prisoner. Then the knight has to joust Sir Breunor, the lord of the castle. When Breunor wins, the knight and the lady are both executed. If Breunor loses (this never happens) Breunor and his wife are executed instead. This is how they do things at Castle Weeping, we’re told.