Sirius will be rewarded with a conspiratorial smirk when he talks about the Slytherins. Remus leans a bit closer and gives him a mild tut as he shakes his head.

"That's not exactly very professional, professor Black," he murmurs, making sure no one else hears them. Because to be honest, he doesn't want Sirius to get in trouble and his first instinct is to make sure it doesn't happen.

It doesn't matter that he doesn't know what has happened to this Sirius, he's still Sirius, some things are obvious.