It had been Ayto, Crimm’s companion from the Scibet, who had come up with a better way. Fishermen had always made their living from hunting, and knew how to think like prey. Ayto watched where the herds had come from. He had a series of bonfires set up along the route, big heaps of rubbish from the Wall, piles of smashed-up furniture and wall panels, kindling made from screwed-up papers and parchments from the Archive. And Ayto had sent out scouts to watch for the approach of the animals. The next time a herd had approached Etxelur the fires had been lit, the hunters had danced and shouted and waved their spears – and the animals, alarmed, had veered in a great mass, heading just the way Ayto had planned, into the maze of frozen-over canals that was the Door. The killing of the trapped, panicking animals had been great.

It had quickly been learned just how much you could do with a dead reindeer. There was the meat, of course, but the skin had endless uses, and you could make tools and clothes-toggles from the bones, rope and fishing line from sinew. For one winter the people of Etxelur had become the reindeer people, and flensed skulls and antler racks adorned the caves on the Wall’s seaward face where people lived now.

The Door had made a tremendously effective reindeer trap. Crimm wasn’t given to thinking too deeply, in his experience it never paid off. But it had struck him that it was almost as if the Door had been designed for just that purpose, and maybe it had been, back in long-gone wintry days.

That had been last year. But this year was different, as the last had been different from the one before. There had been more snow, of course, masses of new stuff that fell and covered the old and, in the spring, once again stubbornly refused to melt. But this year, no more reindeer. Maybe they had gone further south still, in search of summer grass. And the Wall folk, eagerly waiting with their pyres and spears, had seen only a few beasts, including this one solitary specimen. Still, Crimm, from his mound, could see that the moment of the kill was coming, the animal approaching the humans, prey nearing predator, all in silence. Crimm felt his heart beat faster, imagined the splash of blood on the clean snow.

But then his eye was distracted by movement. A black speck crossing the ice, far to the south. For the last couple of years nothing good had come out of the south.

He yelled down to the hunters. ‘Ayto!’

His voice, echoing, startled the reindeer. It looked up, confused. Then it turned and began to run the other way, fleeing from the hunters. Ayto and the rest saw the deer’s white rump as it bobbed away. Some of the men hurled their spears in frustration, even one-armed Aranx.