“I thought the Fourth were meant to be all about headfirst dives and getting all crazy,” said Gideon, who stared hard into every shadow.

“It’s stupid to get killed if it doesn’t help,” said Isaac, tracing his thumb in curious shapes along the doorjamb. “The Fourth isn’t cannon fodder. If we’re first on the ground we need to stay alive … wards were the first thing I learned. When we get shipped out next year, we’ll get them scarified onto our backs.”

Next year. Gideon was taut with impatience, but still spent a couple of seconds grappling with the notion that the gawky teens in front of her would be facing the Empire’s foes at age fifteen-and-whatever. For all that she’d longed to be on the front lines from the age of eight up, it suddenly didn’t seem like such a great idea.

“We wanted to go this year,” said the cavalier, dolorously, “but Isaac got mumps a week before deployment.”

Remembrance of Isaac’s mumps threw them both into gloom, but at least that diluted their terror. In the end Gideon found herself leading them down the hallway marked SANITISER, the place where she had first found Harrow. Their three pairs of feet kicked up huge scuffs of white powder, glowing mixed colours under Isaac’s necrolight, settling down in silent sprays in the panel grouting, grinding to nothing beneath their footsteps. The doors moaned open to the panelled maze of stainless steel cubicles, and the vents moaned too in sympathy, creaking so much that the teens both gritted their molars.

Harrow’s old blood was still here, but Protesilaus wasn’t. They all split up to walk the maze of metal tables, checking beneath them to see if he had lain down for a swift nap, or something equally probable; they prowled rows of metal cubicles, all empty. They called out, “Hello!” and “Protesilaus!,” their voices reverberating thinly off the walls. As the echoes faded, they heard the scuttling noises of air being blown through the vents’ metal teeth. “There’s something here,” Isaac said.

They all listened. Gideon could hear nothing but the sounds of old machinery running in the same exhausted way it had run for thousands of years, kept alive by perfect mechanism and necromantic time. They were no different from the background noises of the Ninth House. She said, “I can’t hear it.”

“It’s not just hearing,” said Isaac, brow furrowing, “it’s more—what I’m feeling. There’s movement here.”

Jeannemary said, “Another House?”

“No.”

“Wards?”

“Nothing.”

She stalked the facility with her rapier drawn and her dagger clutched in her hand. Gideon, stranger to teamwork, worried that if she startled her by accident she’d end up with the Fourth’s offhand in her gut. Isaac said, “Bodies were brought into here—a long time ago. A lot of bone matter. The First feels like a graveyard all over, but this is worse. I’m not faking.”

“I believe you,” said Gideon. “Some of the stuff I’ve seen down here would ruin your eyelids. I don’t know what the hell they were researching, but I don’t like it. Only bright side is that it’s all pretty self-contained.”

“I’m … not super certain,” said the adept. Sweat was beading on his brow.

Jeannemary said, “He’s not in here. Let’s go somewhere else.”

They left the bright antiseptic room of Sanitiser. The lights went off with rhythmic boom, boom, booms as Gideon pressed down on the touchpad that still held little black whorls of Harrow’s blood, and they spilled out into the corridor. Sweat was openly dripping down the sides of Isaac’s temples now. His cavalier threw her arm over his shoulder, and he buried his hot wet face in her shoulder. Gideon again found this difficult to look at.

“Let’s bounce,” said Jeannemary.

As they turned the corner to where the Sanitiser corridor met the main artery, the rhythmic boom, boom, boom of lights shutting down caught up with them. The lights in the grille beneath them winked out of existence, and so did the dully glowing panels above, and so did the bright lights ringing the big square room ahead. They were left in total darkness, every nerve in Gideon’s body singing with fear. She ripped her glasses off to try to cope.

The necromancer was close to hyperventilating. His cavalier kept saying, with eerie calm: “Your wards aren’t tripped. It’s just the lights. Don’t freak out.”

“The wards…”

“Aren’t tripped. You’re good with wards. There’s nobody down here.”

One of the motion-sensor lights struggled back on behind them, a short way down the passage. A ceiling panel threw the metal siding into sharp white relief. It was daubed with words that had not been there a few seconds before, written in blood so fresh and red that there were little drips:

DEATH TO THE FOURTH HOUSE

The light flickered off. After no sleep—after days of threat and grief and panic that would have floored a man twice his age—Isaac lost it completely. With a strangled cry he flared in a halo of blue and green. Jeannemary yelled, “Isaac, behind me—” but he was sizzling with light, too bright to see by, a sun and not a person. Gideon heard him flee into the room ahead of them, blinded by the running aurora.

When her eyes cleared, Gideon was confronted with the biggest skeletal construct she had ever seen. The room was full of it, bluely aflame with Isaac’s light, a massed hallucination of bones. It was bigger by far than the one in Response, bigger than anything recorded in a Ninth history textbook. It had assembled itself into the room by no visible means, since it never could have fit through one of the doors. It was just simply, suddenly there, like a nightmare—a squatting, vertiginous hulk; a nonsense of bones feathering into long, spidery legs, leaning back on them fearfully and daintily; trailing jellyfish stingers made up of millions and millions of teeth all set into each other like a jigsaw. It shivered its stingers, then stiffened all of them at once with a sound like a cracking whip. There was so much of it.

It was cringing away from Isaac Tettares, who had planted his feet wide in line with his hips and was screaming soundlessly in fear and anger. He had thrown his arms out wide as though in embrace, and there was a sodium explosion in the air between him and the room-cramping construct. It left a suction, like he was trying to drag something out of the unwilling creature. Bright blue points of contact appeared on it, and the mass of bone and energy began to lose form, drifting instead toward Isaac, tiny bones plinking down to the grille like rain.

Gideon woke from her confusion, drew her sword and ran. With a gauntleted hand she picked up the nearest stinger and yanked it, then smashed the back of her heavy glove into another, finding a naked shank of legbone and punching it as hard as she could. One of the tendrils of teeth wrapped around her ankle, but she found purchase and stamped it into a corona of molars. Gideon looked behind her to see Jeannemary whipped off her feet by another tendril, lashing out wildly with her feet and her blades. Everywhere she looked was filled with construct: everywhere Isaac’s light touched there was a veritable cancer of bone and tooth.

Gideon bellowed, voice deadened by a thousand million frigging bones:

“Run! Don’t fight it, RUN—”

But the enormous thing slapped another couple dozen tendrils down on the grille, sinuous, and flexed into long sharp wires. Isaac’s blue-green fire fell upon a giant trunk of bone, a skull terrifically mangled into the thing’s only coherent core: a simulacrum of a face with closed eyes and closed lips, as though locked perpetually in prayer. This vast mask loomed down from the ceiling and strained beneath Isaac’s pull. One of the tendrils gave in and was sucked into the vortex that the Fourth House was so valiantly creating. The spirit pinned to it was dissolving, the limb pattering into individual bits, one among hundreds.