Gideon hauled again at the hatch, as though offering up the universe’s most useless act might endear her to the physics of a locked door. His sigh grew sadder and more explosive as he watched her. “You’re winners, you and Nonagesimus both. Hang on—Cam, do a perimeter, please—Ninth, listen. It’s well above freezing down there. That means blood stays wet for an hour, let’s say an hour and a half. Hers hadn’t skeletonised altogether. You with me? She might have spilt it deliberately—although, she’s an osseo, she’s not going to do blood ritual on herself—right, you’re not even pretending to pay attention.”

Gideon had stopped paying attention somewhere around wet and was now bracing both feet to pull: she was pressing down the frame with a foot, distantly taking in every fifth word. Blood. Skeletonised. Osseo. The necro called out, “Camilla, any sign she left while—”

Camilla was on the stairs.

“No, Warden.”

He said to Gideon, gruffly: “Odds are she’s still down there.”

“Then get off your ass and help me,” said Gideon Nav.

This did not surprise or alarm him. In fact, his tightly-wound shoulders relaxed a fraction from black-hole stress fracture to pressure at the bottom of the ocean. He sounded almost relieved when he said, “Sure.”

A jangling object sailed through the air, visible more as sound and movement than as thing. The necromancer failed to catch it: it banged him hard on his long, scrabbling hands. Gideon recognised it as the iron loop that she had been given on the very first day in Canaan House. As he squatted beside her, smelling like dust and mould, she could see that a long key had been put through the loop and was clanking there untidily. There was another, smaller key dangling off to one side, gleaming golden, with an elaborately carved shank and deep pockmarks instead of cuts in the shaft. A key ring? They’d all been given key rings?

Inserted into the keyhole, the first key opened the trap door with a low, hard snap, and together the boy and Gideon threw it open. It revealed a ladder of metal staples down a long, unbelievably dark hole: light shaded in at the bottom, throwing into relief the fact that one slip meant a broken neck along with your broken ass-bones.

A pointing finger appeared in front of her like a spear tip: Camilla’s. The Sixth cavalier had reclaimed the flashlight, and by its glow she could see that Camilla’s eyes were much darker than her necromancer’s: his were like clear stone or water, and hers were the unreflective, fathomless colour of overturned Ninth House sod, neither grey nor brown. “You go first, Ninth,” she said. “Palamedes follows. I bring up the rear.”

It took a full minute to descend that long, claustrophobic tube, staring at the rungs of the ladder with her robes tucked between her knees, sword clanking on metal all the way down—and at the bottom, Gideon was utterly nonplussed.

What lay beneath the trapdoor was a retro installation. A six-sided tunnel lined with dusty, perforated panels stretched out before them. The ceiling was merely a grille that air coolers pumped through and the floor a grille with visible pressure pumps beneath, and the lights were electric bulbs beneath luminous white plastic. There were exposed pipes. The supporting archways contained bulky, square autodoor sidings. This rhapsody of greys and sterile blacks was interrupted over the nearest arch, where, twisting in the dry breeze of the climate cooler, hung a bundle of old bones. Ancient prayer wrappers were ringed around it, and it was the only human, normal touch.

“Follow me,” said the young man called Palamedes.

He strode forward, filthy hem whispering on the dusty-ass tiles. This place ate sound. There were no echoes: they were squashed and absorbed into the panelling. The three of them clanked unmusically down the tunnel until it opened into a big nonagonal room, with passageways radiating out like bronchiae. Letters of brushed steel were set beside each passage:

LABORATORY ONE–THREE

LABORATORY FOUR–SIX

LABORATORY SEVEN–TEN

PRESSURE ROOM

PRESERVATION

MORTUARY

WORK ROOMS

SANITISER

Light wells above made the panelling white; lights from below—little blinking lights attached to huge machines that went down metres beneath the grille, a huge deep way beneath their feet—made the floors softly green. The walls were unadorned, except for an enormous old whiteboard rimmed in metal, printed with lines for a timetable that had not been used in a very, very, very long time. The lines had blurred; the board was stained. Here and there meaningless bits of letters survived: the loop of what might be O or C; the arch of an M; a line-suffixed curve that could be G or Q. But in one bottom corner lingered the ghost of a message, drawn thickly in black ink once, now faded but still quite clear:

It is finished!

The atmosphere down here was oppressive. The air was so dry it made her eyes and mouth prickle. Camilla had one hand on her sword, and Palamedes kept wringing his together, rocking from foot to foot as he moved in a long, slow, 360-degree sweep of the room. At some stimulus, or lack of stimulus, he took a sharp turn toward Sanitiser. Gideon followed.

The short hallway to Sanitiser was floored with panels rather than grille, covered in a powdery build-up like salt, scuffed underfoot and heaped in little drifts. These dunes dissolved like an exhaled breath if kicked.

Quite abruptly there was blood. Palamedes thumbed his tiny flashlight out of his pocket and the liquid gleamed redly beneath the beam. Blood had been spilt, in some quantity, and then smeared heavily away down the hall, leaving a long dark scrape of drying gore. Smaller splatters had dried on the surrounding walls.

The door at the end of the hallway—a huge blast door, metal, with a glass panel set in its centre that was so grimy you could no longer see through it—opened with a touchpad that was also smudged with curls of dried blood. Dried, and drying. Gideon pressed it so hard that the doors twanged open like they were startled.

The first room of Sanitiser stretched before them as a huge, low-ceilinged, white-panelled maze of cubicles: long steel tables beneath the upside-down metal mushrooms of spray heads, and narrow boxes a human could stand upright in. It was fully as big as the grand, destroyed hall of Canaan House. The lights whirred overhead. A panel on the wall blinked furiously as some mechanism in it tried to wake up—it looked like a screen—but eventually it decided better, went blank, and the room was resubmerged in shadow. Gideon was hunting with a dog’s mindless, preternatural panic for a scent, trying to find—

Spatters of blood led her to a big ridged lump in one of the cubicles. This cocoon-looking thing was about the size of a person, if that person wasn’t particularly tall. Before Palamedes and Camilla could stop her, Gideon strode up to it and gave it an enormous kick. Osseous matter showered one side of the cubicle, tinkling away as the spell broke into the oily grey ash of cremains. Curled up inside—hands bloodied, paint smeared, the skin beneath it the same oily grey as the cremains—was Harrowhark Nonagesimus.

Gideon, who had spent the morning planning the wild, abandoned dance of joy with which she would greet Harrow’s dead body, turned back to Camilla and Palamedes.

“I can take it from here,” she said.

Ignoring her, Palamedes pushed past to the broken-bone chrysalis and fished around in its awful contents. He pulled a bit of Harrow’s black robe aside, then the collar of her shirt, past three necklaces of bone chips strung on thread, revealing a startling patch of bare skin—yikes—and pressed two fingers to her neck; he held a hand over her mouth; he said sharply, “Cam,” and she dropped to her knees beside him. She pulled a wallet from somewhere inside her shirt and removed, of all things, a wire. The outer insulation had been stripped from each end, revealing sharp metal tips, and one of these he jabbed into the fleshy part between his thumb and forefinger. It drew blood. The other end he pressed to Harrow’s neck where his fingers had been.