In the mornings on they went, part of an ever-evolving caravan, heading always into the morning sun. At each stop the caravans fissured and split, and new trains formed up for the onward journey. Soon they traded away their camels for horses that would be more suited to the high, mountainous country to come, so Avatak was told. The mule plodded on, apparently unimpressed.

The land became more difficult, steeper, arid for long stretches, and their progress seemed painfully slow. Petty problems slowed them further: illness, scorpion bites, brackish water from fouled springs, lamed horses. Much of the summer still stretched ahead, but old Pyxeas was already fretting about the need to reach far Cathay before the autumn closed in.

One morning, crossing a highland at the foot of a mountain, they heard a deep groaning from beyond the eastern horizon, like the bellow of some tremendous animal, punctuated by sharp cracks. They all knew what this was, the locals and traders from experience, and Avatak and Pyxeas from memories of Coldland. Pyxeas was excited by the sound and insisted they hurry ahead.

They came to a glacier, a river of ice pouring down the mountain’s flank. The back of the great ice beast was littered with rubble, smashed-up rock and timber, and relics of human living: wood panels, posts, what looked like a section of fencing. A river of meltwater gushed from the glacier’s snout, littered with ice blocks, washing across the plain below. There were tremendous cracks and groans as the vast weight of ice pushed and jostled, seeking an elusive equilibrium.

Jamil, Uzzia and the other traders laboured to get the horses and their single mule across the meltwater stream. The sun was high, the air clear, the ice gleamed brilliant white, and the frothy water spreading across the plain below was the colour of the sky. Close to the glacier the stream with its ice blocks was impossible for the animals to cross, and the beasts had to be walked downstream to calmer water. There the travellers cast ropes across, clambered through the chill flow themselves, and then began to lead the laden animals one by one.

Avatak felt guilty not to be down there helping them. But Pyxeas had no regard for these petty human struggles; he had eyes only for the grand, cold drama of the glacier itself.