[Lupin was only responding to the unspoken threat he percieved in Scorpius. The stranger was polite and calm enough, but something felt distinctly off. He couldn't place what.

He's grateful to end their handshake, though doesn't show his eagerness to withdraw openly. There was a game here, and a dangerous one. He needed to save face.]

I make jokes all the time. It's a human thing, and there's a lot of us around here--it might be smart to get used to it.