The professor was completely silent as Jack stood in the shaft of sunlight that came through the tall window. After a few minutes, when Jack began to fidget, he sighed and said, “Enough. Let the hunt begin.”

The twins took turns with the witching rod. It was difficult to hold, and they soon became quite sensitive to its every twitch and tremble — perhaps oversensitive. They spent a lot of time examining empty rooms and unmarked stretches of walls. They opened countless chests, drawers, and doors, the skeleton key working every time. Often Jack heard the distant chime of a clock when he turned one of the keys. Eventually, he realized it must be an echo of some old power, and wondered if the keys had been used by Wardens as well as by their grandfather. That would explain why the key apparently was physically drawn to the locks they presented it with, as though it had a mind of its own.

Unfortunately, when the twins got the chests, drawers, and doors open, they usually found nothing but dust. There were occasional surprises that under other circumstances would have piqued their curiosity: a brass bell hidden under a sagging bed, four pitted cannonballs in a pyramid in one corner of an otherwise empty attic, several coils of rope that rats had nibbled at, a shield leaning up against the side of an empty barrel, even a moth-eaten jester’s hat in a glass case with a label that had faded into unintelligibility.

They did find lots more whales: in carved flourishes on the banisters, on dinner services and cutlery stacked neatly in the lifeless kitchen, even on a handkerchief someone had dropped long years past behind a sagging baseboard. Jaide supposed the whales made sense, given the family’s fortune was made through whaling, but it was still a bit grotesque.

They also found the castle’s medieval toilets.

“Is that what I think it is?” asked Jack, pointing at a piece of wood with a round hole in it, lying flat in a niche that stuck out of the wall in one corner of the castle’s solar.

“It’s a garderobe,” said Professor Olafsson. “Has the future no need of such things anymore?”

“We call them toilets, and yes, we still need them,” said Jaide, looking down the hole. It led to a pit outside the castle walls. A strong draft made her shiver. The air smelled of rain. “I wonder if the Rourkes used these? You know, being super realistic with the history and everything?”

“There were proper toilets in those bathrooms upstairs,” said Jack. “And next to the library. Besides, wouldn’t they stink?”

“Not if properly cleansed,” said the professor. “A few buckets of water every time, mixed with a solution of hyssop and rosemary. Or you could lower a small child with a brush —”

“Okay, okay!” interrupted Jack. “That’s enough about garderobes! Let’s get on with finding the card. We’re running out of time.”

“I’m not getting any twitches,” said Jaide, waving the witching rod slowly across the walls and furniture. The solar was one of the few places where the twins had found anything actually made of gold. Here, it was in the form of a candelabra and a cufflink case shaped like a fish. Downstairs they had found gold mugs in the dining room and a gold pen in the study, looking as though it had dropped on the desk decades ago and never been moved.

“Maybe that’s a good sign,” said Jack, kicking at the foot of a bed in frustration and provoking a rain of dust. “It never seems to point to anything interesting. Could it be faulty, Professor Olafsson?”

“That is a remote possibility,” said the death mask. “The wire mechanism is simplicity itself. The fault might lie in the operator —”

“Are you saying I’m doing it wrong?” asked Jaide, looking under the bed and finding only an ornate chamber pot.

“— or in the nature of the card’s hiding place. What if we can’t find this card because it is not truly here?”

“Huh?” said Jack.

“There are more worlds than we can imagine brushing up against this one, realms separated from ours by the simplest thought, the merest breath. What if the card is in one of those? The witching rod might glimpse it, but we cannot because we lack the key to enter the realm the card occupies.”

The twins glanced at each other. The Compendium had mentioned Professor Olafsson’s ideas about parallel universes and how they were controversial among Wardens, with the majority not believing him. But the twins didn’t want to show signs of skepticism in case he became offended and wouldn’t talk to them anymore.

“We have the skeleton key,” said Jack, hefting the ring in his hand. “Could that help us?”

“I don’t mean that kind of key,” Professor Olafsson said. “These locks aren’t physical. They’re mental. Only with the greatest effort of mind can we unpick them. I was working on such keys when I died, but my work was sadly incomplete.”

“So the card could be here and at the same time … not here?” said Jack, trying to get his head around the idea.

“Exactly. We are surrounded by things we can’t see that are there and things we can see that aren’t. Like salt dissolved in water, or a reflection in a mirror. Have you never wondered where The Evil comes from, what its reality is like? It has its own world from which it attempts to break into ours, a world with its own rules … horrible ones, no doubt, quite inimical to our own.

“I’m not saying that the card is with The Evil,” he added hastily, seeing the alarm blossoming on their faces, “but that it might be somewhere like that. Another world with its own rules, connected to our own by some means of passage that someone fathomed and which we, too, now must.”

Professor Olafsson looked satisfied with that conclusion, but the twins were still frustrated.

“Like a secret passage?” said Jaide.

“Yes, exactly like that, between one world and the next.”

“Do you know if the castle had any secret passages?” asked Jack.

“None that I saw, in the attics or the areas in which I was on display.”

“You wouldn’t put a secret passage where just anyone could bump into it,” said Jaide. “You’d put it somewhere safe, somewhere private.”

“Somewhere like the solar,” said Jack excitedly.

“Exactly!”

Jaide leaped off the bed and began poking things at random — carved knobs on the mantelpiece, gas-lamp brackets and joins — looking for loose panels or hidden switches. Jack did the same, abandoning the mysteries of the witching rod for something more concrete.

“I didn’t mean to be taken so literally,” said Professor Olafsson, jostling from side to side as the twins competed over likely possibilities. “I hardly believe that a passage between worlds would be revealed in such a vulgar way as —”

He stopped talking when, with a solid click, a carved whale sank one inch into the wall under Jack’s insistent thumb, and a panel slid aside next to it, revealing a dark, dank space beyond.

“Oh my,” said Professor Olafsson. “You do appear to have found something.”

Jaide peered inside the hidden panel and saw narrow stone steps leading downward. The walls of the secret passage were wood, once polished but now stained with age and damp. There were brackets for torches, all empty, and the light from the solar petered out after a few steps. Beyond that point, Jaide could see nothing at all.

Jack fared better, thanks to his Gift, but even he could see just ten feet forward, to the point where the stairs turned left. The ceiling was very low, and he was horribly reminded of the sewers under Portland, where The Evil had once chased him. He still had nightmares about those terrible experiences. Here at least there was no slime, and the air smelled stale, not foul. And the odds were that the realm of The Evil probably wasn’t at the end of the tunnel … or so he hoped.

“After you,” he told Jaide.

“You found it,” she shot back. “Besides, you can see in the dark. I can’t.”

He swallowed his fear with a gulp and stepped inside. As though sensing his reluctance, Jaide put one hand on his shoulder and followed closely behind him. He was glad for his sister’s presence. In the sewers he had been entirely alone, and that had been the worst thing of all.

They descended four steps. Behind them, the panel closed with a soft click, plunging them into total blackness.

It was Jaide’s turn to be frightened, and to be grateful for Jack’s confident guidance. Fortunately the dark didn’t last long. Four more steps took them to the corner, and as they turned it, she found that a notch in the wall farther down allowed a sliver of dim light into the tunnel. To her dark-adjusted eyes it was more than enough to see by. As they passed the notch, she saw that it opened onto a room they had visited before: a pantry on the first floor that had seemed utterly unremarkable.

“There might be holes like this all over the castle,” she whispered.

“We should’ve checked the paintings,” said Jack. “You know, like in old movies. There’s always someone peeping through the eyeholes.”

That prompted a creepy thought. What if someone had been watching them as they searched the castle? The stalker might be in the tunnels with them right now….

Don’t be silly, she told herself. There’s no one in the castle but us.

But the creepiness remained as they followed the tunnel down through switchbacks and past several more peepholes. At the bottom was a narrow storeroom, one of several, judging by the arched doorways leading from it, with curving ceilings above, like a vault. There were no chests or drawers, just stuff piled up or leaning against walls in apparently random fashion. Some of it was unidentifiable — implements or machines made from metal and wood, some of it rusted or rotten almost to nothing — but much was eerily familiar, after three visits to the Rourke Castle. It was the legacy of two generations of whaling.

There were harpoons corroded and stained by the blood of all the whales they had killed. There were carving knives as big as scimitars, with grips large enough for two hands. There were hooks and ladles and spades and tubs, along with compasses, cables, and oars that could have had innocent uses, but probably hadn’t, considering the company they were keeping. There were sheets of whalebone in its raw form, which Professor Olafsson called baleen, plus numerous white objects that he assured them were whale’s teeth, carved decoratively by the crew of the long-gone ships.

Jack and Jaide moved among them slowly and carefully, feeling a kind of revolted reverence normally reserved for graveyards and their father’s old record collection. There was other stuff, too — a collection of artifacts from Asia and Polynesia, consisting of leering carved heads and wooden spears, and other artifacts difficult to identify — piled high in places like backyard junk, although once it had been precious to someone, Jaide thought. It might have been an exhibit, in a time when taking such things from the people who owned them was acceptable.

“What’s it all doing down here?” Jaide asked. Echoes whispered back at her like a hundred voices.

“I guess he had to put it somewhere,” said Jack. “Mister Rourke, I mean. With whaling being banned and so unpopular and everything.”

“But why keep it at all?” She flicked open an old journal, the topmost of several stacked in a pile. The copperplate handwriting within was hard to decipher, but it seemed to be a captain’s log from 1891. “He should’ve just thrown it all out.”

“Whaling is banned?” said Professor Olafsson in amazement. “What oil lights your homes, then? What material strengthens your ladies’ corsets?”

“Uh, we don’t do stuff like that anymore,” said Jaide. “Whales are almost extinct. It’s wrong to kill them.”

“Maybe he kept it for a reason,” said Jack, getting out the witching rod. “To hide something else.”

He gripped the wire tightly and swept the business end over a pile of rotting tarps. He tried the walls in case there was another secret passage. He scanned everything he could see, even if it didn’t gleam or couldn’t possibly contain anything.

Nothing — until the rod was pointing at the third entrance on the right. Then the wire twisted in his hand like an eel, so powerfully he almost lost his grip on it.

“Through there!” he said. His feet moved as though of their own accord. The rod was tugging him forward, pulling him toward the doorway.

Jaide fell in behind him, breath tightly held. They entered another narrow storeroom, lit by the faint light shining through two narrow peepholes. This storeroom held more of the same, with one important difference.

Next to a doorway on the other side of the room was a large suit of armor — but this wasn’t the usual plate-and-mail variety. This was made of overlapping leather, gilded at the edges, with a wide skirt and sloping shoulders. The helmet was crested in red, sporting a nose guard and a gorget, a long, spreading collar that protected the neck. Ornate serpent patterns covered the chest and shoulders.

“Chinese,” said Professor Olafsson. “Ceremonial, by the looks of it.”

Jack shushed him. The witching rod was pointing at the suit of armor. He approached warily. The space inside the helmet was dark and empty. Could the Card of Translocation be hidden inside?

They had barely crossed halfway across the storeroom when the rod twitched again, tugging Jack to one side. At the same time, the light coming through the peepholes brightened, and they heard footsteps.

Jaide’s breath stopped in her throat. They weren’t alone!

The beams of light shifted as though someone holding a torch was moving on the other side of the wall. Someone coughed — a man. Jack put a hand over the death mask’s mouth and inched closer to the peephole, Jaide close alongside him. They crowded together and peered through to see what lay beyond.

It was a cellar filled with wine barrels. A man moved among them with a light strapped to his head — like a miner’s lamp but modern, with LED globes. It was hard to see his face for the shadows it cast. His hands held simple L-shaped pieces of wire that Jaide recognized from the Compendium: It was another sort of witching rod, different to theirs but designed to do the same thing. If they were pointed at something magical, the weighted ends would swing together.

“Where is the wretched thing?” the man asked himself.

Jack suppressed a gasp of realization. The face might be hidden, but the man’s voice was immediately familiar.

“It must be here,” muttered Rodeo Dave, pointing the witching rod methodically at each of the barrels in turn.

And Jack understood. It was Rodeo Dave’s rod that their rod had detected — which meant …

Jaide realized before him, but pulled him away a second too late. Rodeo Dave’s rod twitched at the same instant the one in Jack’s hand did. They had detected each other!

Rodeo Dave’s head came up. He stared for a long moment at the unbroken wall before him. The miner’s light shone directly through the peephole. Jack and Jaide retreated from him. Rodeo Dave seemed to be staring right at them.

Jaide’s foot kicked a fallen machete, which scraped along the cobbled floor with a terrible grating noise. Rodeo Dave froze.

“Who’s there?”

The twins acted instinctively. Jack reached out with his Gift to snuff out the miner’s light, while Jaide whipped up an obscuring whirlwind, thick with choking dust. Darkness and grit blinded Rodeo Dave’s sight. He staggered back with a howl, tripped over his feet, and fell heavily onto his backside, blinking uselessly.

“Run!” Jaide hissed, pushing Jack ahead of her.