‘And you see over there . . . the lower Arctophylax sinks, and the nearer to the horizon Cynosura dips, the further east we travel.’

‘You know exactly where we are?’

‘From the stars, and the height of the sun, I can judge with some accuracy how far we are from north to south.’ Quintus smiled, almost apologetically. ‘How far east–west is a matter of reckoning, but if we keep going east we must come to the upper reaches of the Tigris.’

‘There is no true reckoning to be had from the stars.’

The interruption made Valens jump. For such a bulky man, Iudex moved very quietly.

‘They deceive mankind. It is in their nature.’ Iudex spoke with certainty.

‘What do you mean?’ Valens asked.

Iudex tilted his huge, hairless head to one side, as if pondering. Officer or not – was the questioner worthy of an answer? Eventually, he nodded.

‘The Living Spirit captured the demons of darkness. He flayed them, and stretched their skins to make the firmament. Their bodies he fixed as the planets and the signs of the zodiac. The stars have a malign influence on humanity.’

Quintus snorted in derision. ‘Your religion has addled your mind.’

Iudex spread his hands in benediction. ‘The Light shone in Darkness, and Darkness comprehended it not.’

A suspicion slipped into Valens’s mind. ‘You are not a Christian, are you?’

‘Thou shalt not kill, so the Christians say. Sometimes killing is necessary. It is the Lord’s will. I have no qualms.’

Valens was going to ask further questions about his beliefs, but Iudex forestalled him. ‘It is late. We should sleep. Our road is long. There will be better times to put your feet on the path to righteousness.’

*

In the blue light of pre-dawn, the clouds were gone from the peaks of the Singaras, dispersed by a rising wind out of the east. They watered and fed the animals first: three portions of oats to two of hay, chaff mixed in with the hay to stop them bolting the food unchewed. Some of the men gathered camel thorn for fires to warm their rations. The tough twigs spat and burned fast, and gave little heat. Valens ate his hard tack and bacon cold.

The needs of men and beasts satisfied, Decimus oversaw the loading of the mules. They worked in pairs. Everyone lent a hand – Valens teamed with Iudex. There was no opportunity to talk. Cinch – take – break – take. Like the liturgy of a religion, the responses echoed down the line. To properly train a muleteer was said to take a year, but the basics could be learnt in about a month. Frumentarii were resourceful, and these men knew what they were about.