Then they walked on again. A little way out of town they passed a kind of monastery based in caves in a hillside, with walls of brick and clay set up along terraces. Men, clean-shaven and in dusty orange robes, climbed ladders. Monks, they were, Uzzia said, following the teachings of a god-priest called the Buddha. Avatak had seen some of these in the town. He had thought they were beggars; he had seen them imploring for gifts of food and drink, going from house to house.

Now the country opened up once more, and they found themselves on a broad, grassy plain – flat and endless, it seemed, stretching to the horizon, though as they walked they would glimpse worn mountains looming.

‘This is the steppe,’ Uzzia said as she plodded along. ‘A Rus word. You’re in the very heart of Asia now, the core of the world continent – a place where the writ of even mighty empires like Cathay does not run. And it is this land that has always birthed the savage horsemen. The most powerful of all were the Mongols, under Genghis, the first of the great Khans. Now his descendants rule Cathay itself. You’ll see.’

Ferocious the Mongols might be, but for now Avatak saw nothing of them. Their progress was slow, though the country was comparatively easy. Avatak insisted on giving the mule time to feed on the sparse steppe grass.

In an island of lusher, greener country, they came to a substantial city, walled, where green gardens within were fed from springs. This was a place called Lop, Uzzia said. She said they should stay here for seven days to feed, rest and water, to prepare for the next stage of the journey, the hardest stretch yet. The city seemed crowded, a tense, busy place. But Uzzia found them an empty house, and a clean stable for the mule, and vendors soon arrived with sacks of water and wine, hunks of meat, dried fruit and vegetables, pots to cook in.

Avatak said, ‘I don’t understand how we’re paying. We were robbed – you were, they took all your trade goods. And a mountain of trapped rabbits couldn’t pay for all this stuff.’

She glanced across at Pyxeas, who was limping around the house lighting oil lamps. ‘I’ll take you into my confidence. I suppose if anything happened to me it would be a shame to waste it.’

‘Waste what?’

She took her quilted jacket from where it hung on a hook by the door. She showed Avatak fine slits in the fabric, pushed her finger deep inside one of the quilt’s little sewn pads, and pulled out a gleaming stone. ‘A diamond,’ she said. ‘And I have sapphires, a few rubies, some bits of jade and agate, silver and gold for small change . . .’

‘Ah.’

‘This is the best way, in these turbulent times. To convert your wealth into the most portable form. And the most easily concealed.’