Traditionally it's supposed to be really obvious whether or not at any given moment you are talking to a demon! They've got an oppressive infernal aura, and claws or fangs or horns or wings or a tail or unnatural coloration or, generally, the look of a thing that was made according to the same broad template as humans but took a lot of liberties with the details.
The man who steps into Z's field of view has none of these attributes. But his face might be familiar, or his strikingly sweet smile.
"I wasn't expecting to see you again so soon," he says. "What happened?"
(The room is very round; its white walls curve smoothly into a domed white ceiling, with a glowing white globe hanging from its apex, not quite centered above the bed. It doesn't quite have the air of a hospital room, but it's not exactly in the traditional vein of a bedroom either. Sort of in-between.)