“What? Good lord, no. I mean, that’s the kind of madness he believes in. No, I’m just old, Alex. Just old.”

“So, but . . . well, how old is he?”

“I can only really guess at that. Always did look young for his age, even before. I’ve made efforts to find out when he was born, but he’s always covered his tracks carefully. I think I can narrow it down to somewhere between 1785 and 1795. Let’s say he’s about two hundred and thirty. And my sister is around a hundred and eighty-four.”

The car shivered as the old man moved out to overtake.

“Sister?” Alex failed to understand. Then he felt his brain buckle and his skin creep as the moon face zoomed in his memory. “The girl. Zia. The little girl. She’s your sister.”

“Sadly, yes. Ah, are you okay, Alex?” The old man was watching him in the mirror. “I mean, are you okay with me, son? I’m still me, you know. Still old grandad. Just because I’m maybe a little older than you thought, it doesn’t change anything about that.”

“No, I’m okay. I think . . .” Alex fell silent, trying to figure out what he thought. It felt like trying to balance at the middle of a seesaw. On one side, the weight of everything he used to think he understood. On the other, his equally heavy certainty that every word the old man had just said was true.

“Right,” he said, trying to adjust. Once again, he was struck by how calm he sounded. “But how? And I don’t understand. You look old. I mean, not . . . a hundred and ninety . . . but much older than . . . your father. And Zia, she’s just a kid.”

“Oh, that’s simple enough. I stopped taking the potion when I went away from them. To keep the biological age frozen, you have to keep using it, you see. It’s not a one-off thing. You need to top up regularly.”

“Potion.”

“Brew my father concocted. Elixir. You know how he operates. Combination of science and magic and, ah, other learning. He’s from the school that doesn’t recognize dividing lines between any spheres of knowledge: ancient wisdom or modern developments; science, philosophy, or religion; magic or black magic, or whatever else you might care to call it. What they used to call a magus during the Renaissance, and what we might call a Renaissance man today, ha. Shame he’s insane.

“It took him years, but he found his recipe by deciphering various obscure books and manuscripts. He’s amassed thousands of rare works, Alex, dating back to medieval times. Some earlier. Strange books. Lots of Latin and runes and astrological symbols. Instructions on communing with angels and demons. Accounts of opening doorways to other places, with handy woodcut illustrations. You get the idea. You’ve seen some of it yourself. This Shadow Gate business is right up his street.