If there weren't more serious things to discuss here, Gabe could totally make hay with the very notion of William knowing what he felt like. And maybe if he wasn't a tiny bit charmed at the the notion and William's slightly huffy sincerity. Anyway, there were more serious things to discuss. "It's..." he waved a hand, having a similar problem with putting in words. "The grease from magical lock-picks. And probably the remnants of something for getting around Achmed."
It might even have been a shortcut built in to bypass the wards. Someone had got into his workroom. Well, two someone's, but the traces William had left had been almost shining in both their newness and honesty. He'd been obvious. The other someone had taken great pains to hide their passage; Gabe had never even noticed until William had suggested he examine the wards more carefully. The djinn was supposed to record when the wards had been tampered with. But he hadn't.
"On the bright side," Gabe mused, "if anything in there was fucked with, it's probably now also been incinerated."