“Sometimes I forget everything you have been through,” she said finally, and turned around to face forward.

It only took them forty-five minutes to find Plover’s house, aka Darras House, which must have once been in the deep countryside, but now you could get there on a well-maintained two-lane road. Poppy pulled over on the other side. There was no shoulder, and the Jag tilted at a perilous angle.

All four of them got out and straggled across the road. There was no traffic. It was about three-thirty in the afternoon. The grounds were surrounded by a formidable stone wall, and the gate framed, with an almost fussy architectural perfection, a view of a palatial Georgian country house set back deep in carefully tended grounds. Darras House was one of those rectangular English houses made of gray stone that probably conformed to some nutjob eighteenth-century theory about symmetry and ideal proportions and perfect ratios.

Quentin knew Plover had been rich—he’d made one fortune in America already, selling dry goods, whatever they were, before he came to Cornwall and wrote the Fillory novels—but the scale of it was still stunning. It wasn’t so much a house as a cliff with windows in it.

“Jeez,” Josh said.

“Yeah,” said Poppy.

“Hard to imagine somebody living there all by themselves,” Quentin said.

“He probably had servants.”

“Was he gay?”

“Dude, totally,” Josh said.

There was a sign on the gate, DARRAS HOUSE/PLOVER FARM, with a schedule of hours and tours and entrance fees. A blue plaque gave them a capsule biography of Plover. It was a Thursday, and the house was open. A large black bird retched loudly in the underbrush.

“So are we going in?” Poppy asked.

He’d thought they would, on the off chance that they might stumble on something, and so they could say they had. But now that they’d arrived the place felt empty. Nothing here called to Quentin. Plover had never gone to Fillory. All he’d done was write books. The magic was somewhere else.

“Nah,” he said. “I don’t think so.”

Nobody disagreed. They could come back tomorrow. If they were still on Earth.

They trooped back across the road and spread out the map on the hood of the car. The exact location of the house the Chatwins had stayed at near Fowey was a matter for speculation, but not wild speculation. There was a limited number of places it could be. Plover’s books were full of enchanting descriptions of how the Chatwin kids, singly and en masse, ran and skipped and cycled over from their aunt Maude’s house to visit their beloved “uncle” Christopher. Plover had even famously had a little child-size gate built in the wall that separated their properties to let them through.

They had two Plover biographies with them, one a soft-focus hagiography from the 1950s, authorized by the family, the other a hardnosed psychoanalytic exposé from the early 1990s that anatomized Plover’s complex and “problematic” sexuality, as symbolically dramatized in the various Fillory novels. They stuck to that one. It had better geography.

They knew that the Chatwin house was on one Darrowby Lane, which helped, although the Cornish were even less interested in signage than the Venetians. Fortunately Poppy turned out to be excellent at this kind of cross-country dead-reckoning navigation. At first they thought she must be using some kind of advanced geographical magic until Josh noticed that she had an iPhone in her lap.

“Yeah, but I used magic to jailbreak it,” she said.

It was late afternoon, and they’d traversed what seemed like several hundred verdant and Watership Down–esque but stubbornly unmarked and unidentifiable rural byways, and the light was turning bluish, before they settled on a target property, which sat on a narrow lane that wasn’t definitely not called Darrowby and as near as they could tell pretty much had to back onto Plover’s enormous estate.

There was no wall or gate, just a gravel track curving back through the late-summer trees. A square stone post next to it supported a NO TRESPASSING sign. They couldn’t see the house from here.

Quietly Julia read out the relevant passage from The World in the Walls:

The house was very grand—three stories tall, with a façade made of brick and stone, and enormous windows, and endless numbers of fireplaces and window seats and curving back stairs and other advantages, which their London house distinctly lacked. Among those advantages were the sprawling grounds around the house, which included long straight alleys and white gravel paths and dark-green pools of grass.

There was a time when Quentin could probably have said it along with her from memory.

Quentin sat in the car and stared across the road. He couldn’t see much evidence of anything as nice as that. The place didn’t exactly scream “portal to another world” either. He tried to imagine the Chatwins arriving here for the first time, the five of them crammed into the backseat of some sputtering black proto-automobile, more carriage than car, and with a fair amount of locomotive DNA in it as well, their luggage tied to the boot with twine and Victorian leather strappage. They would have been funereally silent, resigned to exile from London. The youngest, five-year-old Jane, the future Watcherwoman, reclining on her older sister’s lap as on a chaise longue, lost in a fog of longing for her parents, who were respectively fighting World War I and raving in a posh rest home. Martin (who would grow up to become a monster who would kill Alice) keeping his composure for the sake of the youngsters, his soft boy’s jaw set in grim preadolescent determination.

They’d been so young and innocent and hopeful, and they’d found something more wonderful than they could ever have hoped for, and it had destroyed them.

“What do you think?” he said. “Julia?”

“This is the place.”

“All right. I’m going to go in. Look around.”

“I’ll come,” Poppy said.

“No,” Quentin said. “I want to go alone.”

To his surprise it worked. She stayed put.

Becoming invisible was a simple idea in theory, but in practice it was a lot harder than you’d think. It had been done, but it took years of meticulous self-erasure, and once accomplished it was practically impossible to undo; apart from anything else you could never be sure you’d reinstated your visible self completely accurately. You came out looking like a portrait of yourself. The best work-around Quentin knew was more like an animal’s protective coloring. If you were standing in front of some leaves, you looked drab and leafy. If you weren’t moving or jumping around, an observer’s eye tended to skate over you. Usually. If the light wasn’t too good. The car door chunked shut in the stillness. He felt the others’ eyes on his back as he crossed the road.

There was something on top of the stone post: buttons. They were scattered in the grass around it too. Big ones, small ones, pearly ones, tortoiseshells. It must be a fan ritual. You come by, you leave a button, the way people left joints on Jim Morrison’s grave.

Still, he stopped and touched each of them, one by one, just to make sure none of them were genuine.

The camouflage spell was unbelievably crude. He picked up a big leathery oak leaf, snapped off a shingle of bark from a tree, plucked a blade of the scanty grass, and collected a granite pebble from the edge of the road. He whispered a rhyming chant in French over them, spat on them, and—the glamorous life of the modern sorcerer—stuffed them in his pocket.

Further up and further in. He stayed off the gravel driveway and picked his way through the trees for five minutes, until there were no more, and then he was looking at Aunt Maude Chatwin’s house.

It was like he was looking back through time. The unpromising driveway had been a feint, a hustle. It really was a grand house; it probably would have qualified as magnificent if they hadn’t just come from Plover’s house. As Quentin got closer the gravel track pulled itself together and became a proper driveway, which clove in two and formed a circle with a modest but still entirely effective fountain at the center. Three rows of tall windows adorned the front, and the gray slate roof was a beautiful profusion of chimneys and gables.

Quentin hadn’t known what to expect. A ruin, maybe, or some appalling new Modernist façade. But the Chatwin house was perfectly appointed and restored, and the lawns looked like they’d been trimmed that morning. It was everything Quentin had hoped for, except for one thing. It wasn’t empty.

That well-maintained lawn was littered with cars. They were nice cars that made the rental Jag look poky by comparison. Yellow light spilled out of the lower floors and out into the mellowing dusk, chased by some nicely judged, not-overamplified early Rolling Stones. Whoever’s private hands the house was in, they were having a party.

Quentin stood there, on the outside looking in, as a little convocation of evening gnats began to gather over his head. It seemed sacrilegious—he wanted to barge in and order everybody out, like Jesus ridding the temple of moneylenders. This was ground zero for the primal fantasy of the twentieth century, the place where Earth and Fillory had first kissed like two cosmic billiard balls. Over the chatter a roar went up, and a woman shrieked and then laughed uncontrollably.

But looking on the bright side, it was a tactical windfall. It was a big enough party that they could mingle in, the girls especially. They wouldn’t sneak in at all, they would walk in the front door. Brazen it out. Then when any suspicions had been allayed they would slip upstairs and see what they could see. He walked back to the car to get the others.

They found a spot for the car on the lawn. They weren’t the least plausible bunch of partygoers imaginable. Quentin had invested in some nice clothes in Venice, charged to Josh’s bottomless credit card.

“If anybody asks just say John brought you.”

“Good one. Dude, are you gonna . . . ?” Josh gestured at Quentin’s appearance.

Oh, right. Probably better not to show up looking like a pile of mulch. He killed the camouflage spell. Crossing the threshold, Quentin closed his eyes for just a moment. He thought of little Jane Chatwin, still alive and at large somewhere. Maybe she would be at the party too.

Josh made straight for the bar.

“Dude!” Quentin hissed. “Stay on mission!”

“We’re in deep cover. I’m getting into character.”

For all that it was a party at Maude Chatwin’s house, it was also just a party like any other party. There were pretty people and unpretty people, drunk people and undrunk people, people who didn’t care what anybody thought about them and people standing in corners afraid to open their mouths lest somebody look directly at them.

Deep cover notwithstanding, Josh revealed himself to be conspicuously American by asking the bartender for beer. He wound up settling for a Pimm’s Cup, which he consumed with an air of disappointed bafflement. But he and Poppy made themselves agreeable to the other guests with an ease and skill that Quentin found awe-inspiring. Genuinely social people never ceased to amaze him. Their brains seemed to generate an inexhaustible fund of things to say, naturally, with no effort, out of nothing at all. It was a trick Quentin had never figured out.As an unattached American male among English strangers, he felt inherently suspicious. He did his best to affiliate himself with small groups and nod along politely in response to people who weren’t especially talking to him.

Julia found a wall to put her slender back against and looked decorously mysterious. Only one man dared to approach her, a tall Cantabridgian type with a half-grown beard, and she sent him packing in terms so uncertain he had to salve his wounds with cucumber sandwich. After a half hour of this Quentin felt he could begin a slow drift toward the stairs—not the grand Tara-style ones in front but a more unassuming, utilitarian staircase toward the back of the house. One by one he caught the others’ eyes in turn and inclined his head. We were just looking for a bathroom? All four of us? Too bad they didn’t have drugs; that would have made a better cover story.

The staircase performed a tight switchback up to the second floor, a hushed and darkened maze of white walls and parquet. The rumble and tinkle of the party was still clearly audible, but hushed now, like distant surf. There were a few kids up here, helling along the hallways and racketing in and out of rooms, laughing a little too hysterically, playing some game nobody knew the rules of, flopping down on the coats when they got tired, the kind of forced pack of one-shot friends that exists on the margins of all grown-up parties.

The World in the Walls wasn’t a how-to manual, and it was irritatingly vague as to the precise location of the famous clock. “One of the back corridors of one of the upper floors” was all the detail Plover gave them. Maybe it would have been better to split up, except that would have violated the basic teaching of every movie ever made. Quentin would have worried that everybody else would slip through into Fillory without him, leaving him behind in reality like the last man standing in a game of Sardines.

Whoever lived here now didn’t use the top floor at all, and it had gone unrestored. Another piece of luck. They hadn’t even refinished the floors—the varnish had worn off them, and the walls were old wallpaper, with even older wallpaper showing through in places. The ceilings were low. The rooms were full of mismatched and broken furniture under sheets. The quieter it got the realer Fillory began to feel. It loomed in the shadows, under beds, behind the wallpaper, in the corner of his eye, just out of view. Ten minutes from now they could be back on the Muntjac.

This was the place. This was where the children played, where Martin vanished, where Jane watched, where the whole terrible fantasy began. And there in the hallway, the back hallway—as it had been written, as the prophecy foretold—stood a grandfather clock.