Sir Lamorak rides off in a huff with Sir Dirant.  They haven’t gone far before they stumble upon an unnamed knight in service of Morgan le Fay, the Queen of Gore.  Lamorak wastes no time in beating this knight up and getting his story.  It’s a whole big thing.

Morgan sent him to Camelot with a magical drinking-horn.  A faithful lady drinks from the horn, she’s fine.  A wicked adulteress drinks from the horn, she spills it everywhere.  Supposedly Morgan’s plan was to embarrass Arthur, what with the whole Launcelot/Guenever thing.  I find this to be a little suspect, given that Morgan mostly fights patriarchy, and this is some classic slut-shaming.  But hey, Morgan as prototypical feminist is interpolation on my part.

Anyway, Lamorak seizes the drinking horn and takes it back to Castle Tintagil, where he tells Mark and the assembled court all about it.  Lamorak pressures Mark to compel all the ladies in the court to drink from the horn, which Mark agrees to.  You’d think this would be because he’s angry at Tristram and possessed of full knowledge about the open secret of Tristram’s affair with the lovely Isoud, but actually Lamorak is just eager to show off the magical might of this miscellaneous magical item he’s recovered, this horn of adulteress detection.  Out of the lovely Isoud and her one hundred ladies-in-waiting, exactly four ladies-in-waiting manage to drink successfully from the cup; the rest (Isoud included) are adulterers.

“Well, clearly the thing to do is put all of these women to death,” announces Mark.  “I’m thinking a big bonfire?”

This does not go over very well with the various knights and barons.  Sure, they all learned that their wives were unfaithful, but they were all being unfaithful with other men’s wives, so it balances out.  “Besides,” a baron points out, “this horn comes from Morgan le Fay, enemy of men and kings.  If we put our wives to death over our, I mean their, adultery, then we’re playing right into her hands!  The lesson here is that we should ignore adultery.  And probably spit on Queen Morgan if we ever see her.  But we definitely shouldn’t burn women to death for sleeping with men their husbands haven’t given them permission to sleep with.”

Now I get it!  Very clever, Morgan.  Very clever.  Good ol’ Morgan le Fay.  I should never have doubted you.

Nothing comes of this interlude, except that Tristram takes it as a personal affront that Lamorak would bring in the drinking horn like that.  In Tristram’s mind it is all about Lamorak wanting to take Tristram down a peg by arranging for the lovely Isoud to die.

With Mark unable or unwilling to have the lovely Isoud burned at the stake, she and Tristram grow bolder in their love.  Tristram’s cousin, Sir Andred, last seen spying on the lovers, spies on them again.  This time instead of running and telling Mark, which didn’t work, he gets a lynch mob of a dozen knights together.

How they pivot directly from “let’s not put adulterers to death” to “let’s put these particular adulterers to death” is not addressed.

Andred and his mob storm the lovely Isoud’s bedchamber and grab Tristram while he’s half-asleep.  They tie him up and carry him off to present to Mark as a criminal caught in the act.

CUT TO a high cliff overlooking the sea, at a little chapel, where Tristram stands surrounded by forty knights.

“Any last words?” Mark asks him.

“Just that I’m an all-around excellent knight, and a patriot of Cornwall.  Remember all that stuff I did earlier in this book?  Slaying Sir Marhaus and freeing us from the yoke of Irish oppression?  You remember.  I’m the best, you guys suck by comparison, yadda yadda.  Mainly I just want to say I’m disappointed in my cousin Sir Andred.  Wanting me dead is one thing, but assembling a lynch mob to arrest me, and holding me here with forty knights?  Weak.  Weak move, buddy.  It’s a good thing we’re related, or else this probably would have gone down worse for you.  Although if we were the only two men left alive, I’m sure we’d get along, because then you’d be scared of me.”

“You jackass!” screams Sir Andred, and lunges at Tristram with a sword.  He just can’t take the taunting!  I can’t say I blame him.  Tristram postulated that Andred would, in a state of nature, become Tristram’s slave, which is pretty aggressive as taunts go.

What follows is an action sequence wherein Tristram, despite having one knight holding his bound left hand, and another knight holding his bound right hand, defeats Andred and a dozen other knights.  For part of it, Tristram wields the knights holding him like they were flails, swinging them around against their will.  But then he rips free and just swordfights the rest of them.

Tristram defeats the knights around him, but Mark and Andred have essentially limitless reinforcements, Tristram is just one guy, and also he’s still in his nightshirt.  So he flees into the chapel, and bars the door while a hundred knights and other folks gather outside.  While they break down the doors in the front, Tristram goes out the back.  Which involves leaping into the sea from atop a craggy cliff.