Yaz swung her head from side to side, trying to take it all in, trying and failing to keep her bearings in case she should need to leave in a hurry. The glowing bands overhead kept distracting her, fascinating her eye and putting her in mind of the shimmering veils of light that haunt the polar night. The Ictha called those dragons’ tails though it seemed each tribe had its own story to tell about them.

“Down here.” Arka led the way into a ravine in the bedrock. Rough steps had been carved into the stone and the sound of rushing water rose from far below.

Yaz brought up the rear, stepping cautiously, unused to having rock beneath her feet. Somehow it felt more treacherous than ice. Pinpricks of light broke the darkness ahead of them. Yaz shivered, not so much from the dampness of her clothes but from the thought that this was her life now. Rock and wet ice. She tried to imagine how anyone could live down here not just for days and weeks but for decades, without the ocean to supply hides and fur, sinew and oil, food and fuel . . . all the materials a people needed to construct their lives.

“This is the hothouse.” Arka’s voice drew Yaz from her thoughts and from focusing on her feet as she negotiated the last of the steps. The woman stood before a structure made from neither rock nor ice nor bone nor hide. Yaz had never seen anything like it. She found herself gawping and took comfort that at least the others seemed similarly amazed.

“What is it?” Yaz was the first to find her words.

“The hothouse,” Arka said. “Follow me.” And she ducked inside through what seemed to be a tent flap but didn’t look like one.

“It’s a door,” said an older girl, suddenly scornful now that she realised she knew something the rest did not. She went in after Arka. One by one the others followed.

Yaz came last, running her fingers over the walls and “door.” They were flat like stretched hide though much thicker, vertical like the cliffs of the Hot Sea, hard like rock, smooth like bone. The whole structure sat upon a ledge with the ravine carrying on down to unknown depths, and backed against a rock wall. The small girl, Maya, went through ahead of her and Yaz followed.

“Gods below!” The blast of heat that met her was like nothing Yaz had ever experienced. As if every oil lamp the Ictha owned were lit and placed side by side in the same tent. She joined the others, noticing that unlike the rest of them the thinner of the two boys wasn’t wet or shivering. He had a narrow face, high cheekbones, and, beneath a shock of black hair, dark eyes with a haunted look to them.

“You come wet into the world and the next time you get wet will be your last.” Arka’s tribe clearly shared some of the Ictha’s sayings. “That’s how it is up there where we came from. Down here things are different.” She stepped aside and they saw behind her the rocky cave that the small building fronted. The space was both large and crowded, and it was lit by the light of stars set in what looked to be bowls of glass, a thing only Mother Mazai owned, and then just a small disc of it. For a moment, her vision still blurred by the heat, Yaz thought it was people crowding the space beyond, but she soon saw that only the skins they wore hung there, on lines strung from the ceiling, dozens of sets.

“We dry our clothes here. Hang yours on the wire.” Arka pointed to a line strung across the width of the cave. She walked into the centre, pushing aside sets of hanging skins as she went and setting them swinging. The shadows swung too and for a moment it looked again as if they were people, the Ictha perhaps, dancing for the sun at the end of the long night. Arka clapped her hands. “Hurry!”

She turned her back on them, bending to retrieve something from the floor. When she turned to face them again she seemed surprised that none of them had moved. In a silence broken only by the chattering of teeth she lifted the object she’d retrieved. A clan’s wealth in iron, a squat, heavy cylinder of the stuff, thick-walled and gripped by two bone handles. Deeply etched symbols covered the outside. Yaz knew that the priesthood had a writing that they used to put words on hides. That had always fascinated her. The idea that words, such fleeting things, gone almost as they left your lips, could be trapped and lie there bound in black lines inked into permanence such that they could outlive the one who gave them life. But these symbols were something else again. Like the ice stars they seemed both more real and more distant than the world around them. Complex as the many-legged spider-fish that crawl beneath the sea ice, each was different from its neighbour and yet the same. Each tangled her eye, trying to draw her through . . . to somewhere.

“If you don’t warm up soon you may well never warm up.” Arka frowned at them. “What? It’s a pot. You’ve seen a pot before, surely?”

Yaz hadn’t.

Arka set the iron tube on the floor and using a long metal rod she took one of the glass bowls from its niche in the wall, putting it on the floor. With a small scoop at the end of the rod she removed the star from the bowl and dropped it into the iron pot. Immediately the symbols carved into the metal began to glow. The heat radiating from them made Yaz’s face burn. It was as if she held her hand just an inch from a lamp flame. “Hang those clothes up! Now!” Arka barked the order like a woman used to being obeyed. “You stay there, Thurin.” She raised a hand to the black-haired boy as he moved forward with the others.

Yaz stayed with Thurin, though she backed away from the heat. Even Arka seemed surprised by its fierceness, raising an arm to shield her face. “I must have used too large a stone . . . ah . . . there, it’s easing off.” She relaxed, then lifted her voice to address them all, falling into her role as their teacher. “The sigils set into the iron convert the energy the stone gives off into heat.”

“I call them stars,” Yaz said. She tried to look anywhere but at the naked flesh being exposed. The Ictha generally only took something off in order to replace it with something warmer. They would shed layers in their tents but never retain fewer than three. Only in the Hot Sea would they strip, and there the mists shrouded everything, hiding one end of a small boat from the other. The drying, when the Hot Sea closed, was a time of great hardship and more died in that handful of days than in the rest of the year together. “Stars. Not stones . . .” She faltered under Arka’s hard stare.

“Some do call them that. Heart-stones, core-stones, ice stars, it’s all the same. Strip.”

Yaz hesitated. With the exception of Thurin the others had moved among the hanging skins, seeking privacy.

“Why isn’t he wet?” She pointed an accusing finger at Thurin, who frowned, almost in pain.

“Because he didn’t drop today. He’s here for . . . other reasons.” Arka folded her arms and looked Yaz up then down. “Do the Ictha have something under their hides that the rest of us don’t?”

Yaz scowled. If she protested further they would all be watching her as Arka wrestled her out of her wet skins. With a snarl Yaz walked into the area where the clothing already strung up offered the most shelter. She stripped off her outer skins, struggling with tight knots. Her innermost layer was sewn on, requiring a knife to remove and a needle to replace. She would not need it down here out of the wind. The wind was the true killer. It amazed her not to hear it. Its absence was a silence battering at her ears. Once when Yaz was little the wind had stopped. Not dropped or weakened, but stopped. It was a thing that even the grey among them had never seen. The elders thought that it might be the end of the world. Some wept. Some tore at their hair. And then the wind blew again and it was as if that moment of stillness had never been.