Newt talks quickly, animatedly, hands waving about as he turns to face Sirius, walking backwards the whole while. It's entertaining, really. Mad, but in a good way. Sirius's favourite way, honestly. His lips twitch into a smile that then immediately slides away into shock at Newt's reply.

"Harry Potter?" he repeats, slowing to a stop right in the middle of the corridor.

Like most things in this city, it doesn't make any sense. When had Harry been stranded on an island? He's never mentioned any such thing to Sirius. And, as far as he's aware, Harry's never dated much at all either. Of course, there's every likelihood he's simply kept that part of himself secret from his godfather in much the way Sirius has kept his own quiet from Harry. But if this man is already married to the woman Harry once dated then... well, that had to have been one whirlwind romance, surely.

He squints a little. "You're certain? Harry?"