“You apologise to me?” she bellowed. “You apologise to me now? You say that you’re sorry when I have spent my life destroying you? You are my whipping girl! I hurt you because it was a relief! I exist because my parents killed everyone and relegated you to a life of abject misery, and they would have killed you too and not given it a second’s goddamned thought! I have spent your life trying to make you regret that you weren’t dead, all because—I regretted I wasn’t! I ate you alive, and you have the temerity to tell me that you’re sorry?”

There were flecks of spittle on Harrowhark’s lips. She was retching for air.

“I have tried to dismantle you, Gideon Nav! The Ninth House poisoned you, we trod you underfoot—I took you to this killing field as my slave—you refuse to die, and you pity me! Strike me down. You’ve won. I’ve lived my whole wretched life at your mercy, yours alone, and God knows I deserve to die at your hand. You are my only friend. I am undone without you.”

Gideon braced her shoulders against the weight of what she was about to do. She shed eighteen years of living in the dark with a bunch of bad nuns. In the end her job was surprisingly easy: she wrapped her arms around Harrow Nonagesimus and held her long and hard, like a scream. They both went into the water, and the world went dark and salty. The Reverend Daughter fell calm and limp, as was natural for one being ritually drowned, but when she realised that she was being hugged she thrashed as though her fingernails were being ripped from their beds. Gideon did not let go. After more than one mouthful of saline, they ended up huddled together in one corner of the shadowy pool, tangled up in each other’s wet shirtsleeves. Gideon peeled Harrow’s head off her shoulder by the hair and beheld it, taking her inventory: her point-boned, hateful little face, her woeful black brows, the bloodless bow of her lips. She examined the disdainful set of the jaw, the panic in the starless eyes. She pressed her mouth to the place where Harrow’s nose met the bone of her frontal sinus, and the sound that Harrow made embarrassed them both.

“Too many words,” said Gideon confidentially. “How about these: One flesh, one end, bitch.”

The Ninth House necromancer flushed nearly black. Gideon tilted her head up and caught her gaze: “Say it, loser.”

“One flesh—one end,” Harrow repeated fumblingly, and then could say no more.

* * *

After what seemed like a very, very long time, her adept said:

“Gideon, you need to promise me something.”

Gideon wiped a thumb over her temple, tidied away a stringy lock of shadow-coloured hair; Harrow shuddered. “I thought that this was all about me getting a bunch of concessions and you grovelling, but you called me Gideon, so shoot.”

Harrow said, “In the event of my death—Gideon, if something ever does get the better of me—I need you to outlast me. I need you to go back to the Ninth House and protect the Locked Tomb. If I die, I need your duty not to die with me.”

“That is such a dick move,” said Gideon reproachfully.

“I know,” said Harrow. “I know.”

“Harrow, what the hell is in there, that you’d ask that of me?”

Her adept closed heavy-lidded eyes.

“Beyond the doors there’s just the rock,” she said. “The rock and the tomb surrounded by water. I won’t bore you with the magic or the locks, or the wards or the barriers: just know that it took me a year to walk six steps inside, and that it nearly killed me then. There’s a blood ward bypass on the doors which will only respond for the Necromancer Divine, but I knew there had to be an exploit, a way through for the true and devout tomb-keeper. I knew in the end it had to open for me. The water’s salt, and it’s deep, and it moves with a tide that shouldn’t exist. The sepulchre itself is small, and the tomb…”

Her eyes opened. A small, astonished smile creased her mouth. The smile transformed her face into an affliction of beauty that Gideon had heretofore managed to ignore.

“The tomb is stone and ice, Nav, ice that never melts and stone that’s even colder, and inside, in the dark, there’s a girl.”

“A what?”

“A girl, you yellow-eyed moron,” said Harrowhark. Her voice dropped to a whisper, and her head was dead weight in Gideon’s hands. “Inside the Locked Tomb is the corpse of a girl.

“They packed her in ice—she’s frozen solid—and they laid a sword on her breast. Her hands are wrapped around the blade. There are chains around her wrists, coming out of her grave, and they go down into holes by each side of the tomb, and there are chains on her ankles that do the same, and there are chains around her throat …

“Nav, when I saw her face I decided I wanted to live. I decided to live forever just in case she ever woke up.”

Her voice had the quality of someone in a long dream. She stared through Gideon without looking at her, and Gideon gently took her hands away from Harrow’s jaw. Instead she sat back in the water, buoyed by the salt, her eyes starting to sting from it. They both floated there for a long time in amicable silence, until they pulled themselves up and sat, dripping, on the side of the pool. The salt was crusting up their hair. Gideon reached over to take Harrow’s hand.

They sat there, wet through and uncomfortable, fingers curled into each other’s in the half-light, the pool interminably lapping at the cool tiles that surrounded it. The skeletons stood in perfect, silent ranks, not betraying themselves with even a creak of bone against bone. Gideon’s brain moved and broke against itself like the tiny wavelets they had left, the water lurching restlessly from side to side, until it came to a final conclusion.

She closed the gap between them a little, until she could see tiny droplets run down the column of Harrow’s neck and slide beneath her sodden collar. She smelled like ash, even smothered under litres and litres of saline. As she approached Harrow grew very still, and her throat worked, and her eyes opened black and wide: she looked at Gideon without breathing in, her mouth frozen, her hands unmoving, a perfect bone carving of a person.

“One last question for you, Reverend Daughter,” said Gideon.

Harrow said, a little unsteadily: “Nav?”

Gideon leaned in.

“Do you really have the hots for some chilly weirdo in a coffin?”

One of the skeletons punted her back into the water.

* * *

For all the rest of that evening they were furtive and unwilling to let the other one out of their sight for more than a minute, as though distance would compromise everything all over again—talking to each other as though they’d never had the opportunity to talk, but talking about bullshit, about nothing at all, just hearing the rise and fall of the other one’s voice. That night, Gideon took all her blankets back to the unedifying cavalier bed at the foot of Harrow’s.

When they were both lying in bed in the big warm dark, Harrow’s body perpendicular to Gideon’s body, Gideon said: “Did you try to kill me, back on the Ninth?”

Harrow was obviously startled into silence. Gideon pressed: “The shuttle. The one Glaurica stole.”

“What? No,” said Harrow. “If you’d gotten on that shuttle, you’d have made it safe to Trentham. I swear by the Tomb.”