Gabe watched him a moment longer, before nodding, just a little. "One day you're telling me about that," he said - or maybe threatened - easily, but he didn't dwell on it now, pulling a sheet of parchment (a letter) out of the book and setting it on top, in case he needed the reference.
"Yes," he continued, moving on to business, all serious, "you drink it. I'm here, and I'll look after you, and it won't be as... intense. As strong. You'll probably be able to stay aware. And it won't last as long. But it'll still be weird. You might want to sit down first."
First time Gabe had had the stuff, he'd started out sitting and woken up lying on his stomach, tangled up in the carpeting. He'd been happy enough just to wake up still in touch with who and where he was. And William had done this out of curiosity at the Ministry? The alternative - that he'd done it still at school - was a little too much to contemplate. Gabe sort of wanted to find a time-turner, go back and smack everyone involved. But then he'd have had to find another way to convey the pathogen, and fuck knew how long that would've taken. Too long.