Alone in his dressing room, Robert attempts to prepare his apology. Two minutes hadn't passed after his public censure of Cora that he recognized his monumentally poor decision.
In the bedroom she wears a prim expression that means he is in trouble. It figures that she would be upset at being told off in front of the servants. She carefully arranges the blankets across her lap, self-contained and grim, and perhaps a little wounded. She knows how to stoke his guilt without much effort.
"It gave your mother the best night she's had since Christmas."
That, he does not doubt.