Okay, so, at this point things go more or less how you’d expect.  Launcelot heads over to Guenever’s chambers.  Mordred and the other knights hide, then listen at the door.  When it sounds like Launcelot and Guenever are in a compromising position, Mordred and Agravaine briefly argue about who’s going to do the actual bursting in on them, and decide against anyone risking getting cut down by being the first knight in.

Instead, Mordred pounds on the door and shouts for Launcelot.

Immediately Launcelot and Guenver realize the jig is up.  They’ve had a good run, but now it’s over.

“Don’t try fighting us!” shouts Agravaine, through the door.  “We’re all heavily armored and there’s fourteen of us!”

Launcelot throws himself backwards on the sheets.  “This is awful,” he says.  “Here I am, bereft of weapons and armor, can’t do anything.  Unless…” He looks up at Guenever.  “You don’t happen to have another sword lying around, do you?  Or armor?”

“You know I don’t!”  Guenever fights back sobs.  “It’s all over!  It’s all over.  Whatever will become of us?”

“I don’t know.”

“If you could escape, that would at least be something.”  She leans against his back, resting her head on his shoulder.

Launcelot chokes out a protest.

“No, no, you know it’s true.  Whether you die or escape here, they won’t hurt me immediately, I’m the Queen.  They put me on trial, they schedule the execution, you would swoop in at the last moment and rescue me.  You’ve done that twice before.  But if you’re dead…”

“I can’t abandon you!  And I won’t!  And I can’t!  I can’t because I don’t have any arms or armor to escape in!”

“Maybe there’s a way around that…”

Eventually, since Launcelot isn’t coming out, Agravaine and Mordred realize they’ll have to go in.  The door is barred, so the knights outside take turns trying to batter it down.

Just as Sir Colgrevance is about to slam his shoulder against the door, Guenever gives Launcelot the high-sign, and Launcelot unbolts and opens the door, such that Colgrevance stumbles forward into the chamber!  Then Launcelot slams the door shut again, before any more knights get in.

Colgrevance, off-balance from falling through the doorframe, rises to his feet and turns, just in time to see Launcelot’s fist bashing Colgrevance’s face in.

“Now, take his sword and his armor and put it on,” instructs Guenever.

Launcelot straps the dead knight’s armor onto himself.  “Listen, if I don’t make it, go to Bors and beg him for protection.”

“Don’t worry, you’ll make it,” says Guenever, and kisses him.

“Well, let’s see if God is on my side,” says Launcelot, and then he unbars the door.

Long story short: he kills everyone except Mordred, whom he badly wounds and leaves for dead.