There's whole strange worlds opening up to Keltham, though he's not at all sure he's understanding them correctly. The notion of having a woman you can do as you please with - well, there's the version where you pay a sex worker so that you don't have to worry about their pleasure except insofar as it pleases you to do so, a sexual asymmetry balanced by a financial asymmetry going the other way - or by knowledge going the other way, in the variant Ione offered him - but the notion of a woman who doesn't allow you but wants you to do as you please, wants you to hurt her -
He'll sort out later what's going onside his mind. He may be ordinarily accustomed to knowing every little detail of what goes on in there, but he doesn't have to sort it out right now before having sex.
Keltham grips her hand harder, because he felt an impulse like that, and pulls her after himself toward the stairs going down, because that feels like the right thing to do.