The problem with Mulder is, he doesn't make a move this time. She kissed him, and he kisses back, but he doesn't so much as try to cop a feel.

In the moment, it's enough that he's able to be here with her, maybe. Maybe. He wants more - of course he wants more - but nothing's happening to him below the waist tonight, and he's stymied by the desire to give her more than he has on offer.