That little step backward had Sirius stopping short of actually reaching Remus and tackling him to the ground like he might have once done -- and had planned on doing until, well. Now.
He wasn't stupid. He'd been paying at least a little attention to everyone else around here - how they all knew each other, but didn't quite all at the same time. Like everyone was from a different time or place, but were still connected somehow. It was a lot to wrap his head around but -- well. Remus did look a little older. And not exactly in a rough werewolf night kind of way. Although maybe there was some of that too, now that he was looking closer. Sirius was pretty good at knowing that look by now. Really good, actually.
"...Ah. I mean. I'm not not here?" He raised his hands, looking at the fronts and backs of them, as if he was suddenly unsure. "What's this all about? I know I've been off a few days. Not on purpose, mind. I just ended up here. But I was on my way to meet you all." If Remus was mad, there was no chance for the rest of them, Sirius figured.