A heavy old door stood at the end of the corridor. There was a grille in it at the height of a man's head, but Carmen was too short to look through. There was no number above it. She stood beside Ward as he rummaged through the keys, watching the corridor, the barking iron held in both hands. He settled on an archaic iron skellington key. It was the only one with no number stamped on it. He put the key in the lock and turned it, and a heavy clunk came from inside the door.

They pushed through and found themselves on a landing lit by a bal-oil lanthorn. Damp steps led down to what she dimly perceived was a corridor. Ward closed and locked the door behind them, his face pale and drawn, his eyes big and dark.

"You okay?" she said.

He didn't reply, or even look at her, but brushed past her and proceeded down the steps. Taking a deep breath, Carmen followed.

The corridor at the bottom was lit by the same lanthorns, and below each stood a stout oaken door, banded with iron and dark with years. The doors were low, as if made for children, and Carmen remebered that the people of olden times had been shorter than they were now. The end of the corridor was lost in gloom, in which a few lanthorns glowed like sullen stars.

Ward had stopped at the bottom of the steps. He seemed incapable of moving forward, like a lapp before a searchlight.

She took his hand and he started at her touch. She spoke the old lie. "It's okay."

"I don't know where it is."

"We'll find it. Come on."

The doors were all unlocked. The chambers beyond were small and claustrophobic, containing nothing but a drain in the floor, a dead lanthorn on a wall, and a table or chair or both. The air was chill and damp. Carmen had been worried there might be Brothers down here performing their unspeakable work, but she heard no sound. From the moment Ward closed the door at the top of the stairs a thick cloak of silence had fallen. Carmen wondered how long a prisoner would stay sane down here.

She was conscious that they were running out of time, but Ward slowed as they progressed down the corridor, as if reluctant to reach it. He stopped before the last door without pushing it open. She saw him swallow.

"It has to be this one," she whispered. "We've searched everywhere else."

"It is."

She realised he had known it all along. Perhaps he had searched all the other chambers in the hope that he wouldn't have to look inside this one. She wanted to say something consoling, but there was nothing she could say that wouldn't be a lie.

He pushed the door open with a sudden movement like ripping a bandage off.

There was nobody inside. Carmen's eyes fell on the terrible chair, which seemed to crouch over the drain, its arms like human limbs scarred by some fearful disease, its leather straps dark with old sweat and blood.

Ward seemed afraid to look at the chair. His attention was focused instead on a dim square shape that seemed to float in the gloom of the chamber's far wall. He had been strangely sure that they would find the door to the Arcane Vault down here. Had he known all along? For a door it was: Carmen could make it out before she was halfway across the chamber. It was smaller again by half than the one they had just passed through, set in the wall at about the height of her hips, and constructed not of oak, but some dull grey metal. A face had been forged in its centre, the face of a woman surrounded by flames. A pagan symbol. The Brotherhood had long ago erased all such symbols from sight and mind, so she thought it strange to find one down here.

Her first thought had been that the door was made of cast iron, but when she touched it gingerly she found it softer and less cold than she had expected.

"They put the prisoners' bodies in here," Ward said suddenly, "so they don't have to take them up to the Crematorium."

The State Crematorium was a bleak building at the edge of the city, not far from the prison. It serviced Bareheep's entire population – indeed, nobody was allowed to dispose of their dead any other way. Transporting bodies there would have been conspicuous, so Ward's theory made sense. It certainly looked like the door of a furnace.

"There's a sign here," Carmen said, using the sleeve of her coat to wipe a little square of metal set into the wall beside the door. It was so black with grime that she hadn't seen it at first.

"What's it say?" Ward said.

"Um. DANGER."

Of course it does, she thought. It struck her as odd that the sign wasn't specific about what the danger was. "Ward, I don't like this."

"Me either," he said. "But the dice are through there. I can feel them now. Up ahead – not far." There was a current of excitement in his voice.

"But what's in -"

"Look, you should go back. I've got this. You can still get out before the Reds come. You've got the barker."

"It's too late. They're already here."

Ward gave her a long, contemplative look that she wasn't sure she liked. There was something calculating about it.

She set her jaw. "I'm coming with you."

He seemed about to protest further, but shrugged instead. He turned to the door and grasped the wheel in both hands. He had to give it a hard jerk to get it moving, but after that it turned smoothly. When the wheel stopped he paused and took a deep breath. Then he pulled the door open.

And died. The end.