"I don't even have a dungeon," Papyrus protests. Where would he have one? In the penthouse? It's entirely too high in the building for that. Unless the humans of Wismuth have very different building regulations.

But, as intriguing as the local zoning laws might be, he's getting caught up with inconsequential nonsense. Which would be fine, if it was distracting enough people. But here and now? It's just Sans.

...In a strange place, with no ground, no gravity, and no apparent exit. If he handles this badly, would Sans get away, and leave him trapped here? That would be even worse than being stuck back at the carnival.

"And that's not important! Stop distracting me." Papyrus exclaims, then forces himself to calm down a little. Spreads his arms imploringly, trying to draw Sans' attention back to him - look, his hands are empty of bones or fresh dust, nothing to attack with. They're still just talking. "The important thing is... Well, I could try to ma-- help you understand what I'm feeling! So you feel it, too. Then you can decide, yourself."

Probably Sans would protest if Papyrus frames it as making him do anything, considering. And... he's not completely sure if his powers work like that. But they do offer influencing emotions, pushing specific sorts of hallucinations, and so on. It might work.