Jupiter sent for Fenestra, who reluctantly met them at the entrance to the Battle Street Wunderground station. She was to escort Morrigan, Jack, and Hawthorne back to the Deucalion while Jupiter attended to the mysterious business of the safeguard pact, whatever that was.

“Don’t let them out of your sight,” Jupiter told Fen for the umpteenth time as he returned from the ticket desk. “No detours, no distractions—straight home to the hotel, no side trips or delays of any sort, understand?”

Fen rolled her eyes. “Oh, but I was going to stop to buy ice cream and puppies.”

“Fenestra…” he said warningly.

“All right, keep your beard on.”

He turned to Morrigan, Hawthorne, and Jack. “Right, you three. It’ll be crowded down there. Stay close to Fen and don’t wander off. Fen, best take the Rush Line to Lilith Gate and then change onto the Centenary Line. That’ll get you to Island-in-the-River; you can catch the Brolly Rail from there straight to Caddisfly Alley. You lot—got your brollies?”

The children nodded.

“But the Viking Line goes directly to Island-in-the-River,” said Fen.

Jupiter shook his head. “Chap at the ticket desk says there’s a delay due to a Viking horde attack in one of the tunnels. They’ll be hours sorting that mess out.”

“Rush Line it is,” she agreed. “Come on, you three.”

They descended into the busy station and pushed through the turnstiles. Fen, who was too large to go the normal way, jumped over the top. An indignant ticket collector made to tell her off, but she hissed at him and he immediately went about his business.

As they traversed tunnels and stairwells, Hawthorne kept looking over his shoulder at Morrigan, desperate to ask about her trial, but it was too noisy. Morrigan caught his eye and shrugged, mouthing the words I don’t know.

When they finally got to the platform, Fen pushed through the crowd to the yellow line at the front, parting the commuters like wheat stalks in a field. Hawthorne, Morrigan, and Jack each grasped a tuft of her fur and tried to keep up, apologizing to people as they elbowed past.

“Slow down, Fen,” said Jack. “You’re going to trample people.”

“If people are in my way they deserve to be trampled,” grumbled the Magnificat. “This is just what I need, after the ridiculous day I’ve had—to babysit you three in a packed Wunderground. The Deucalion’s been a mess all day, people coming and going and making noise. We’ve had workers in to sort out the wiring in the south wing, and Kedgeree’s had those ridiculous ghost hunters back yet again.”

“Ghost hunters!” said Hawthorne, looking excited.

“I thought they got rid of the ghost,” said Morrigan. “Back in summer, remember? They did that exorcism.”

“And yet despite their really top-notch sage waving,” Fen said dryly, “our gray man is still hanging about the south wing, spooking people. Walking through walls and disappearing around corners. The staff have even given him some funny name—oh, what was it?”

“I haven’t seen any gray man,” said Morrigan.

“So you shouldn’t, you’ve no reason to be in the south wing while these damned renovations are going on.” Morrigan exchanged guilty looks with Hawthorne and Jack but said nothing. They still hadn’t told anyone about Morrigan’s accidental visit to the south wing on the night the shadow escaped. “It’s the builders who keep complaining about him, they say they hear him from the next room, and when they rush in to see who’s there, he just disappears into the Gossamer.”

“Hear him doing what?” asked Jack.

“Singing or—no, humming. That’s what they call him. The Humming Man. Ridiculous.”

Morrigan felt a sudden lurch, as though she’d missed a stair. The gray man. The Humming Man. Walking through walls in the south wing, disappearing into the Gossamer. Like a ghost.

She knew instantly how Ezra Squall had been getting into Nevermoor. It was like a light had been switched on in her head and she could at last see clearly.

“The Gossamer Line!” she cried.

“The what?” said Hawthorne.

“The Gossamer Line—that’s how he’s doing it, that’s how he’s getting into Nevermoor,” she said.

“How who’s getting into Nevermoor?” asked Jack. “What are you talking about?”

“Mr. Jones—Ezra Squall—he’s the gray man, the man who hums! That’s why people think there’s a ghost—he’s traveling here on the Gossamer Line, he can walk through walls!”

But her voice was lost beneath a high-pitched whistle and whoosh of steam as their train pulled up to the platform. Scowling, Fen nudged Morrigan and the boys into the first carriage. They had no trouble getting seats, since the other passengers had huddled at the opposite end, happy to give the giant yellow-eyed Magnificat a wide berth.

When they were settled, Fen leaned in close, shoving her great gray head between them. “Watch what you talk about in crowded Wunderground stations,” she growled. “The Gossamer Line’s supposed to be top secret.”

“But Ezra Squall is using it,” hissed Morrigan, glancing over her shoulder to make sure no one was listening. “We have to tell Jupiter. There is no ghost, Fen, it’s Ezra Squall—he’s the gray man!”

“Ezra Squall?” Fen dropped her voice even lower. “The Wundersmith Ezra Squall? Nonsense. He was banished from Nevermoor Ages and Ages ago.”

“It’s not nonsense! I saw him myself. He was in the lobby the day the chandelier crashed, and I spoke to him in the south wing one night last summer—”

“What were you doing in the south wing?” Fen demanded.

“—and he came to watch the Black Parade on Hallowmas.”

“It’s true,” said Hawthorne, nodding fervently. “He was there, I saw him too.”

“Dame Chanda showed me a picture of Squall from a hundred years ago and it’s him, Fen—he looks exactly the same, he hasn’t aged a day! That’s how he’s gotten around the ban, by leaving his body in the Republic—the border guards, the Ground Force, the Royal Sorcery Council—none of them could detect him floating around Nevermoor, because technically he was never here.”

“If that’s true,” said Jack, with a deep frown, “if it really is the Wundersmith and he really is getting into Nevermoor on the Gossamer Line, then… why?” His wary eyes flicked over to Morrigan. “What does he want?”

“Maybe he’s trying to find a weak spot,” said Hawthorne. “Somewhere he can break back into Nevermoor.” He gave Morrigan a significant look, silently encouraging her to tell them about Squall’s apprenticeship bid. He was right, she thought. She had to tell someone, and who knew when Jupiter would return?

“Fen, I think I know what—” Morrigan began quietly, but the Magnificat cut her off.

“This is rubbish! Even if he was riding the Gossamer Line, he couldn’t hurt anyone. He couldn’t even touch anyone. It’s impossible to make physical contact with anything through the Gossamer.”

“Fen, listen,” said Morrigan. “I know what Squall—”

“He is the Wundersmith, Fen,” Jack interrupted. “There must be plenty of stuff he can do that other people can’t.”

“I’m telling you, it’s impossible.”

“Fen, listen to me!” Morrigan shouted.

Suddenly the lights in the carriage flickered and the train slowed to a halt. The passengers all groaned.

“Why have we stopped, Daddy?” asked a little boy halfway down the carriage. “Why aren’t the doors opening?”

“Just another stupid delay, son,” said the man, sighing the defeated sigh of a seasoned commuter. “Mouse on the tracks or something.”

The lights flickered again, fading to black and then stuttering halfheartedly back to life. There was a mechanical-sounding squeal and a voice spoke over the public-address system.

“Good evening, ladies and gentlemen. Seems we have some sort of signal interference up ahead. Shouldn’t be long before we’re moving. Thank you for your patience.”

The lights flickered again. The seats vibrated and the handrails shook.

Morrigan looked around—nobody else seemed to notice. She heard a rumbling from the tunnel and moved to the back of the carriage to press her ear against the wall.

“What are you doing?” demanded Fen.

“Can’t you hear it?”

“Hear what?” asked Hawthorne.

“It sounds like… like…”

Hooves. It sounded like the rumble of hooves bearing down the Wunderground tracks, echoing in the tunnel—then the screeching bray of a horse, the baying of hounds. The sound of a shot being fired.

Morrigan stumbled backward, falling over the seats. “Run!” she yelled. “Everyone get back, they’re coming!”

But there was nowhere to go. The carriage was packed, and the train was stopped in the middle of the tunnel. Morrigan turned to see the crush of the crowd surrounding her, dozens of puzzled faces—including Hawthorne, Fenestra, and Jack, all looking worried.

“Morrigan, what are you talking about?” said Hawthorne, but his voice sounded so distant, so quiet compared to the thundering rush of the Hunt of Smoke and Shadow. “I can’t hear anyth—”

And suddenly, nothing but smoke, nothing but a thick, swirling mass of shadow and smoke surrounding her, filling her lungs. Her feet were swept from under her and she was lifted into the air, carried along by the Hunt, the triumphant sound of horns deafening. She held tight to her black umbrella, clutching it as if it might somehow anchor her to the ground.

Morrigan had never been in the ocean, had never even seen it in real life, but this, she imagined, this was what it would be like to drown, to be swept away by a violent wave and tumbled over and over and over until there was nothing, only darkness and shadow and black, black, black…