But back to Lance and Guen looking out of that window.
They're singing—isn't that sweet? Remember that they're old, also, so this scene is quite touching.
Lance wants to *ahem* visit Guen in her bedchambers that night, but she says no. Arthur's around, and if he finds out, he'll have to kill them.
He then asks her to run away with him—which, apparently, he's now been asking her for years.
She's like, "Man, don't start up with that again."
Guenever tells Lancelot that if she runs away with him, Arthur will have to act, and he'll gather up his knights and lay siege to Lancelot's castle, and lots of people will be hurt and killed.
Plus, it would make Arthur miserable.
Oh, dang. Arthur has arrived during this conversation, but is too good to eavesdrop, so he immediately leaves.
Lance says he should just go away again, but the last time that happened, he went insane. He doesn't think his nerves can take it again.
Then, Arthur truly enters the room, with a page coming beforehand with plenty of light—to give them warning.
Arthur tells them he's been visiting the Gawaines, and that they were having a fight. Lucky nobody got hurt!
The conversation turns to how Lancelot doesn't really have a home, even though many women have thrown themselves at him and some have even proposed to him. He's still a hot commodity, that Lancelot.
The King gets all serious, and tells Lance and Guen a story from before he married Guen.
And the bombshell drops: he reveals to them that he had previously slept with Morgause, and that Mordred is his son.
Guen and Lance are forgiving. They don't think he's evil, because he didn't know it was his sister.
But, wait. That's not all! Arthur (as a young man of nineteen) allowed himself to be talked into issuing a proclamation that ordered that all babies born at a certain time had to be put onto a big ship and floated out to sea. This was to destroy the evidence.
Mordred was saved, though.
But Arthur dreams of all those other babies.
The King knows that Mordred is against him, and will one day get him killed. He can't just kill Mordred (as Lancelot advises him to), because then he'd be a big fat hypocrite. The King must abide by his own laws and ideals.
Chillingly, Arthur notes that a true, just king must be willing to execute his friend. And his wife. And that's just what he'll have to do, he tells them, if his best friend and wife are guilty of a crime against the kingdom.
Arthur warns them to just not let Mordred get anything on them that would force his hand. Too late!
Plus, Mordred has a good motive: he could gain the throne if anything happens to Arthur (since Guen has no kiddos).