Nona stood with Ara, Jula, and Ruli, catching their breath, staring at the exits, Ketti and Darla still climbing behind them.

“I want to get under the convent,” Nona said. She blinked. She hadn’t been intending to speak, but now the words had left her mouth she realized it was better that the truth was out. For three years she had seen the only route to revenge on Yisht to be training. To make herself into a weapon suited to the task of finding then destroying the woman. Neither would be easy. The empire was large, and Yisht expert at hiding, deadly when found. Nona had been very lucky in their first encounter and had still only just survived. But Joeli’s taunting had put into Nona’s mind the idea that there might be some clue at the spot where Hessa died. Something the nuns had overlooked. Something her friend had left for her alone. It was a very faint hope. Too faint perhaps to justify exposing her companions to such dangers . . . but Joeli’s words were an itch that refused to be scratched. “Hessa’s name is so important to you? And yet you’ve never even visited the spot where she died.” The accusation repeated in her mind, an echo that grew rather than died away.

“I need to visit the shipheart vault.” Nona spoke the words into the silence that had followed her first statement.

“Because we won’t be in enough trouble just for being in the tunnels,” Ruli said. “We should go where we’re more likely to be caught and will have broken more rules.”

Jula frowned. Despite her cleverness sarcasm always seemed to go over her head. “But—”

“I’m banned from leaving the convent until next seven-day in any case,” Nona said. “So if I’m right under it I’ll be breaking fewer rules.”

“Go back to the vault?” Ara asked, raising her lantern to inspect Nona’s face. “That’s madness. Abbess Glass will throw us out. You know what she said about the undercaves!”

“I have to.” Nona had to see it for herself. She had to set her hands to the spot where Hessa had died. Perhaps some clue remained that would help her find Yisht. “I have to. For Hessa. I felt her die. The rocks. Yisht’s knife. I felt all of it. If there’s justice to be had, or revenge, it starts there, where it happened.”

“I don’t want to go near the convent. The sinkhole’s too close.” Ketti got to her feet behind them after finishing the climb. “There could be tunnel-floods.” She shuddered.

“I still say they’ll have the undercaves blocked off.” Darla followed Ketti into the chamber, brushing grit from her habit.

“Maybe. But it’s as good a direction to explore as any other,” Ara said. Nona thanked her silently.

“I don’t know . . .” Darla shook her head. “The abbess wasn’t joking when she put the undercaves off-limits. She wrote it in the book and everything . . .”

“That was over two years ago.” Ara came to Nona’s defence. “Plus, if they didn’t know Yisht was there for all those weeks and she was going to and fro from her room, they won’t know we’re there if we come from underneath for a quick look. Right, Nona?”

Nona nodded. She owed it to Hessa. She had let years slide by and done nothing to avenge her. Her friend had died and Nona had hidden in the convent, well fed, cared for, whilst Yisht walked the world with Hessa’s blood on her hands. But though the Corridor might be a narrow girdle to the globe it was still too wide for a lone child to find a woman like that who didn’t want to be found. And Yisht was an ice-triber. She might be anywhere in the vastness of the ice. “I can’t do this alone.” The gate to Shade class had a sigil-scribed lock now: the thing would have to be blown off its hinges to gain access without the key. Coming at the Dome of the Ancestor and the shipheart chamber from below was the best option.

“I’ll help.” Jula spoke up, her voice thin in the cavern’s void.

Nona offered her a smile. Jula put an arm around her shoulders for the briefest hug.

“So . . .” Nona, even less at ease with physical affection than Jula, waved a hand at the tunnel mouths.

“That one.” Jula pointed to the leftmost tunnel, boulder-choked and leading down. She had an instinct for direction below ground that had proved uncanny. “Though it doesn’t look very safe.”

Ara led on and they followed, stepping over fallen rock, some of it still jagged. After a hundred yards or so the passage broadened and became a cavern so wide it swallowed their light and gave nothing back. For a moment Ara halted and they all held quiet listening to the silence and to the drip . . . drip . . . drip of water that was somehow part of the vastness of the silence. Nona glanced about at the novices around her, all illuminated on one side and dark on the other, and for an instant found herself outside her body, suddenly aware of herself as a tiny mote of life, warmth, and light in the black and endless convolutions of the cave system. Now more than ever she felt the irony that the Rock of Faith, named for the foundations of their religion, lay rotten with voids and secret ways, permeable and ever-changing.

“We should go across,” Jula said, her voice small in all that empty space. She didn’t sound as if she wanted to.

Ketti marked the wall with her chalk and drew an arrow on the floor.

“We should follow the wall. We’re less likely to get lost,” Darla said.

Ara took them to the left, staying close to the wall. Stalagmites rose in small delicate forests, stalactites descended in curtains where the cave curved down, glistening with an iridescent sheen like the carapace of a beetle.

“Stop.” Ruli turned and stared into the darkness beyond the lanterns’ reach. Nona stopped, the others too.

“What?” Jula raised her light.

“Didn’t you hear it?”

“No.” Darla loomed beside her, her shadow swinging.

“Something’s out there, coming for us,” Ruli said, wide-eyed.

“There’s nothing living in these caves,” Darla said. “We would have seen bones or dung. What did it sound like?”

“Dry.” Ruli shivered.

“Dry?”

“I want to go back,” Ruli said.

Ara advanced a few yards, lantern high. “There’s something here.”

Nona crowded forward with the others, leaving Ruli in deepening shadow.

“What is it?” Ketti frowned.

To Nona’s eye it seemed that a shadowy forest of misshapen stalagmites covered the cavern floor, some curving over in ways that such growths are not supposed to.

“Bones.” Jula saw it first.

From one instant to the next the scene switched from one of confusion to one of horror. Skeletons, calcified like those back in the niche, but more thickly: dozens of them.

“Some of these have been here for an age.” Ara pointed to a stony ribcage from which straw-thin stalactites dripped, and to a skull distorted by the weight of stalagmite growing upon it, like a candle from which half the wax had run.

Jula bent over to inspect something by the wall.

“We really need to go!” Ruli called at them, not having moved from where she stood. “Can’t you feel it?”

“I don’t . . .” But then Nona felt it and held her tongue. Something scraping at the edges of her senses, a dry touch from which her mind recoiled.