Jon followed William and after a moment admitted, "I kind of accidentally got lost? Thought I saw Clover, followed her and then took a down staircase when I heard some familiar moaning. Not the brightest idea of the day, but," he shrugged, sentence trailing off.
Having had some time to really think about it, being stuck in the great hall for so long and all, Jon had come to the conclusion that all of this could have been stopped if he'd been able to find Tilly earlier this week after that weird incident in the courtyard. Which meant that this was his fault, at least in part. It also meant that when he thought he'd seen Clover, he'd stupidly followed just to stop thinking about it. He'd also spent that last year or so traveling to get away from the memories of his dead girlfriend. Avoidance, Jon knew, was something he excelled at.
"The potions room, huh? Anything in particular you're looking for?"