Get out the microscope, because we’re going through this poem line-by-line.
[...] there was one less than three
"In my quiet room that night, and we were gay;
Till sudden I rose up, weak, pale, and sick,
Because a bawling broke our dream up, yea
"I looked at Launcelot's face and could not speak,
For he looked helpless too, for a little while;
Then I remember how I tried to shriek,
"And could not, but fell down; from tile to tile
The stones they threw up rattled o'er my head
And made me dizzier; till within a while
"My maids were all about me, and my head
On Launcelot's breast was being soothed away
From its white chattering, until Launcelot said:
- Guenevere counts up the number of people who were in her room that night. Instead of just saying "there were two," she says, "there was one less than three."
- (We can do the math, obviously, but why doesn't she just come out and say "there were two of us"?)
- Everything was great for the two of them (or the one-less-than-three of them) until suddenly Guenevere started feeling all faint and weak.
- Their cozy little "dream" was broken up by "bawling" or crying.
- Launcelot looked as "helpless" as she did, and then she started trying to "shriek."
- Was she afraid? Of what? She doesn't say.
- She couldn't actually get any sound out when she tried to "shriek," and she fainted instead.
- She came to with her head resting on Launcelot's chest and her ladies-in-waiting surrounding her.
- She starts to tell us what Launcelot said at that point, but cuts herself off.