Tristram gets tired of sneaking around Tintagil, avoiding Mark. He decides to confront his uncle, and to that end, mounts up with arms and armor. As he rides forth from Tintagil, with the intention of circling around and riding back into Tintagil all splendid and awesome, he bumps into another knight on his way into the castle.
“Yo, stranger,” says this knight. He’s Sir Gingalin, son of Sir Gawaine (so Sir Gawaine has an adult son!).
“Let’s joust!” Gingalin cries. Young and eager, he’ll joust at the drop of a hat. The kid runs at Tristram, breaks a spear, Tristram knocks him upside the head with a sword, boom, that’s that.
King Mark sees this happening — he was out hunting or something, and came back just in time to see a strange knight knock down another strange knight. Mark rushes to Gingalin’s side, pulls his helmet off. “Sir Gingalin! I know you! It’s me, Mark! It’s going to be okay!”
Tristram panics and flees, even though Mark didn’t get a look at his face and Gingalin doesn’t know him from Adam.
Sir Tristram rides off into the forest, where he meets one of his men, Sir Fergus. This is Tristram’s third henchman so far, after Sir Lambegus and Sir Sentraille. Fourth, if you count his old tutor Gouvernail, who continues to follow his boss around and help him into his armor and so on. Maybe it’s me, but I think Malory could have folded these dudes into a single henchman.
Anyway, Fergus greets Tristram. Fergus had no idea Tristram was in Cornwall, and not still back in Brittany! What’s new, Fergus wants to know?
This triggers a massively disproportionate response in Tristram, who breaks down sobbing. He just loves the lovely Isoud so much! And she’s married to Mark! Tristram collapses into a puddle and Fergus can’t rouse him! He just lies there crying, for days.
Eventually, though, Fergus gets him back on his feet, by promising to go to Tintagil and check in on the lovely Isoud for him. On the way there, he bumps into Palomides’s latest lady-friend, oh, let’s call her Maureen.
“I’m looking for Sir Tristram,” says Maureen. “Seen him?”
“Yeah, well, keep it under your hat but he’s having a major depressive episode right now,” says Fergus.
“Dang,” says Maureen. “Where is he?”
“In such a place,” says Fergus. By which Malory means Fergus tells Maureen where he left Tristram, but it’s not important enough for Malory to deign to share that information with us.
Fergus and Maureen split up. Fergus goes to Tintagil, where the lovely Isoud has taken to her bed and spends all her time wailing. Maureen goes to wherever Tristram is, where he’s doing basically the same thing. Maureen tries to cheer Tristram up by seducing him, but all does is get him back on his horse riding off to Sir Adtherp’s castle. Remember Sir Adtherp? He saved Isoud’s life in Chapter 30 of Book VIII, then died of his wounds after Tristram abandoned him in Chapter 33? He had a castle? Yeah. Tristram gets to that castle, where he meets Adtherp’s widow, Angelica Adtherp. Maureen goes with him.
“Tristram, is that you?” asks Angelica, but Tristram only sobs.
“It is him, yes,” says Maureen.
“Poor you,” says Angelica. “Pining over the Queen, still, huh? Let’s get you a nice hot bath.”
Malory explains that Tristram taught Angelica to play the harp (Tristram is the best harpist ever, remember?) and so she’s well-disposed towards him. She and Maureen strip Tristram and bathe him and ply him with sweetmeats and wine and harping and invitations to venery, but Tristram just lies there. Late that night he sneaks away, leaving his armor and stuff at Castle Adtherp, taking along only a harp.
And for the better part of a year — nine months! — he lives as a naked harp-playing crazy hermit in the woods. His only companions are shepherds, who sometimes offer him food and drink, and sometimes beat him with sticks for fun, because they think he’s a lowly mad hermit. Which he basically is.