All three boys cringe at the sound of Sirius being slapped.

The entire library, in fact, goes dead silent. (Even more silent than it usually is, with Amity Root around.)

"Bloody fucking hell, Perdita!" Sirius booms. It's clear he doesn't give a fig for their current location. "Yeah, well I've been through with you from the second week of this ridiculous farce!"

"I — yeah, I think so," James says.