Ayto said, ‘Need to be kept on this side, dogs, where they’re useful. We ought to set up a base over here.’

Crimm nodded. ‘For now, suppose you stay with the sled – Himil, was it? Aranx, you two others, stay with him and start preparing the stuff to haul over. And keep an eye out. In the meantime, the rest of you, come on over. Urnrn, Uncle Pyxeas, it’s quite a climb—’

‘And quite beyond me, I’m sure.’ He turned to Avatak.

With practised ease, Avatak bent, took Pyxeas at the waist, and straightened up with the scholar limp over his shoulder. Nelo helped, throwing a blanket over Pyxeas.

Crimm grinned. ‘I can help you.’

‘I’ll be fine,’ Avatak said. And so he would be; he and the old man in his charge had been through worse than this together.

Crimm went up first. He wore heavy mittens and carried a small axe that he used to knock ice off the ladder rungs. When it was his turn, Avatak took care to get a firm grip with hands and feet at each step. He worked his way up, breathing steadily, letting his muscles warm. He had ridden the sled too long, he hadn’t had enough to eat for many days, and he was not in the best condition, but he could do this. Transferring from one ladder to the next was more tricky, trying to support himself on ice-coated, guano-stained ledges, holding the old man securely with one hand while reaching for the next ladder with the other. But he made no slips.

Pyxeas hung limp, passive, utterly trusting. Perhaps he was asleep.

They took a break on top of the Wall. Crimm had sacks of fresh water that he passed around. Pyxeas was set down on a blanket; he seemed more exhausted than Avatak.

The huge sculptures arrayed along the Wall roof, the old monoliths, the tremendous heads of long-dead Annids, the slim spires erected by more modern generations, had mostly survived, though their features were masked by snow. And from here a view of the Northern Ocean opened up. The level of the sea had evidently fallen, but it was still higher than the land, you could see at a glance; the Wall was still serving its most ancient and basic purpose of saving the land from the sea. On the sea itself, a strip of deep-blue water close to the Wall face gave way to thin ice floating in great patches. People were working on the ice, Avatak saw, looking down. One man sat by a mound on the ice that must be a seal’s breathing hole. Further out there was a boat, silhouetted against the brilliance of the white ice behind. These were Northlanders learning to live like Coldlanders, he supposed. Further out still, icebergs, silent and stately as Cathay treasure ships, were trapped in thickening sea ice.