The Masqueraders by Georgette Heyer

There was no means of telling what John, that stolid creature, made of the situation. His young master and mistress suspected him of being deeper in the old gentleman's secrets than they were, but he had never a word to say on the matter. When my lord had made his first startling appearance they came home and told him of it, and awaited some show of surprise. It was not forthcoming. John gave a grunt and said that he had doubted but that the old gentleman would arrive soon. As to the manner of his arrival, John seemed to think it natural enough, and he never failed thereafter to give my lord his title. The old gentleman had greeted him with an affectionate smile, and a hand carelessly outflung. John had looked beneath his brows and said gruffly that the affair of Master Robin must be seen to. He further volunteered the opinion that Robin's present guise was unseemly. As for Miss Prue, the sooner she was got out of this coil the better. John had a grim way with him, but they had none of them the need ever to stand in doubt of his devotion. Nothing could abate the supreme belief in himself that my lord held, but certainly he used fewer extravagancies with his servant than with his children, and would condescend to listen to John's disapproving words. But not even John could hope to make much impression on that magnificent mind. My lord waved a hand, and promised ultimate success.

"You're playing a game I don't understand, my lord," John said severely. "It's more of your playacting, for sure, but why you should do it, sir, I can't see."