What changed everything was not how they treated her.

It was how they treated Lupita.

Because Karl’s sneer, that this was why you don’t give the cleaning staff too much leeway, they start thinking they own the place, revealed something the rudeness to Clara had not: that his contempt was not a momentary lapse aimed at one tired stranger, but a settled worldview, a habitual disdain for an entire class of person he considered beneath him, extended reflexively even to a woman who had just shown more grace than he possessed.

And that was the line.