Panic. Nervousness. Attempts at diverting the conversation. This all points to Jaskier being full of shit, and that's one of the scents that Geralt doesn't like on him. Lying. He doesn't like it when people lie to him, and he certainly doesn't like it when Jaskier lies to him. Usually, that's because Jaskier's lies come to bite him in the ass in some stupid, angry husband-shaped way.

Jaskier's hands clap over his mouth before he can get the last word out, but fuck is basically one of Geralt's favorite words, so he knows the shape of it even from someone else's mouth. So that's what's gotten Jaskier so upset-- he saw the two of them in the aftermath of the house collapsing, when they had had some kind of... victory fuck? Glad-to-be-alive sex? Something like that. There was a lot of adrenaline involved, and she had been very beautiful sprawled among the pillows and debris, and the effects of his djinn wish would've just been kicking in.

She had still been very beautiful when Geralt had left her sleeping there, too.

Geralt's mouth twists a little at the revelation. Is he thrilled about it? No. Can he do anything about it? Also no. Jaskier saw what he saw, Geralt can't change that. He can't un-fuck Yennefer, no matter how much the bard might want him to.

"Didn't take you for a voyeur," he says, walking into the room to hang up his cloak. No sense standing at the door. "Is this going to be a problem?"