4. Aha!
They went to an extremely expensive restaurant, the kind of place that by all accounts should run credit checks on the patrons before seating them, though no one said a word to them until they'd sat down. A fresh-faced waitress turned up immediately, bearing a bottle of Reisling Auslese and Aziraphale's foie gras, with lentils.
The angel cooed over his plate. Crowley scowled into his glass.
"Let's see that book, then," he said, once the wine had kicked in. Aziraphale obligingly reached into his coat pocket, but when his hand touched the contents he frowned. "What?"
Aziraphale pulled out a book. It was larger, thicker and decidedly older than he remembered it. He turned it over in his hands.
"This isn't the book I left the shop with," he said. He set it on the table. "I must have picked up a different one..."
"But you never put it down," said Crowley, quietly. "You put it in your pocket. I saw you."
"Then where'd this come from?" Aziraphale asked, poking the cover of the book. He pushed it toward Crowley. "And where'd the other book go?"
Crowley picked up the book and opened it, and yelped.
"They're alive!" he cried, tossing the thing back to Aziraphale as if it were, indeed, alive and kicking. He pointed after it. "The pictures! They move."
They did, indeed. Aziraphale stared at what looked like a photograph of children in brightly-coloured robes, flying about a football pitch on broomsticks. Every so often, one of them would stop and wave at him.
"It's remarkable," breathed Aziraphale.
"It's magic," croaked Crowley. "And that goes against everything we - you - stand for."
Crowley didn't stand for much. If anything, he would occasionally recline, with disinterest.
Aziraphale closed the book and looked at the cover. He held it up for Crowley to see.
"Hogwarts: A History," he read.
"There we have it, then," sighed the angel.
Crowley shook his head.
"How can that be, though?" he asked. "You know as well as I do that this... this magic business, with the witches and warlocks and whatnot, goes against HIS will. I mean, it doesn't bother me any, but how can a world with you in it have a world with this as well?"
"Hmm," murmured Aziraphale. He stared at the book cover, tracing the little designs around the edges with a finger, seemingly lost in thought. Crowley took the opportunity and relieved him of the rest of his lunch.
"You're right, of course," he said, after a moment. "This isn't His will... however..."
His eyes widened, and Crowley knew an epiphany when he saw one.
"What?" he asked, through a mouthful of girolles mushrooms and quail's egg. "Wossit?"
Aziraphale beamed like a star over a desert. "That's IT. It makes sense, it's not His will, but it's HIS will... emphasis on the 'his,' you see..."
Crowley swallowed. "Whose will?"
The angel looked triumphant. "Adam's," he said. "Adam Young."
"I'm not following."
"You said it yourself. It's a children's novel," said Aziraphale, tapping the tome in front of him. "I don't remember buying any book like that, which means that more than likely it was put there, when Adam... you know."
"Put the world back the way it was."
"Right, which means it was something he'd read, and... and what if he read it and he liked it? I mean, really, really liked it." Aziraphale's eyes twinkled. "Loved it, even? Enough to start believing in it?"
Crowley stared.
"Don't you see?" said Aziraphale. "The only way a world like this could exist along side our world is if Adam were the one who'd, you know, rearranged things so that it could. Because he wanted it to."
"You're saying that the boy brought that book to life?" asked Crowley, nearly choking on a lentil. "That's preposterous."
"It's-"
"If you say ineffable I'll stab you with my fork."
"-no different than rain forests springing up where there weren't forests before," said Aziraphale, a little guiltily. "Or Atlantis turning up after all those years buried in ocean and legend. Or-"
Crowley waved a hand. "Alright, alright. I get the idea." He looked at the book. "That doesn't explain the book, though. I know you left with that other one, so. Where'd this come from?"
The angel blushed.
"Might be my fault," he said. "Er, my bookshop, that is. Adam put everything back the way it'd been before - except for the children's books - and I expect he wouldn't change anything else because-"
"-he knows you don't like change," finished Crowley, with a smirk. "And when the book left the shop-"
"-it changed, because a fictional book about Hogwarts wouldn't fit into a world were Hogwarts were real."
Crowley rubbed his head. "This is so ludicrous, it almost makes sense," he said, wearily. "Right, so. If all this is true, then what the hell are we supposed to do about it?"
Aziraphale slumped a little. "I don't really know," he sighed. "I suppose we're to watch over him. Guardian angels - er, supernatural entities, or something to that effect."
"Wonderful." Crowley grunted. "I'm supposed to follow him to wherever this school is, I know that much."
"As am I." Aziraphale drank quietly for a moment. He opened Hogwarts: A History again and paged through it. "This looks promising at least," he said, after reading a few paragraphs here and there. "It'll help us know where to start."
Crowley drained his glass. "Where do we start?" he asked.
Aziraphale looked dubious. He flipped to the front of the book and peered at the first few pages.
After a moment, he scratched his head and looked thoughtfully at Crowley.
"I'm not sure I know where this is," he said, "but have you ever heard of anyplace in London called 'Diagon Alley'?"
Crowley closed his eyes, and the waitress returned at once, with another bottle of wine.