There had been no way out, nothing for it but to betray his comrades. Unlike the bandits, the Arabs had been purely fortuitous. If the raid on their encampment had gone wrong, it could have been the end of the expedition. He had trusted in his horse and his skill at arms to get him clear of the disaster. Last-stand heroics did not feature in his thinking. There was money in his belt, and he spoke Aramaic. It was not far back to the Tigris. Get across Mesopotamia and he would be back in the empire.

Against the odds, they had all got away unscathed. Once the nomads were on their trail, he had dropped a couple of bits of equipment to mark their route. In retrospect he was glad that Valens had seen the water bottle and had taken the rear, which had prevented him leaving any further signs. Drawing the tent-dwellers down on them might have fulfilled his orders, but what use was that if he himself did not survive?

Now the Arabs were left behind, some new scheme was necessary. What would happen should Valens meet with some misfortune? There was no formal second in command. All of the men thought the whole venture ill-advised. Several openly wished to abandon the mission. With Valens gone, most likely there would be much heated debate, and then the expedition would break up in acrimony. Once separated, it might be possible to ensure that few, if any, of its number made it back to Zeugma.

Someone was scrambling up from the dry watercourse. His watch was over. The hours had passed quickly. He rose, grunting with the effort, and tried to stretch some of the ache out of his muscles and arthritic joints. Hercules’s hairy arse, I’m tired.

‘Libertas,’ he gave the challenge.

‘Pietas,’ came the response.

As if called by his evil imaginings, Valens walked up the incline.

The sentry felt the hilt in his hand. A couple of rapid movements and the unsuspecting young officer would be dead. There would be no outcry. All finished in a moment.

Not now. He forced himself to relax, release the hold on his weapon. The river was not deep enough to bear away the body. Anyway, the disappearance could not be explained.

‘Don’t move!’ Valens hissed.

Guiltily, his hand moved back to the hilt.

‘Quiet!’ Valens’s head was tipped to one side. ‘Hear that?’

The sentry cocked his head, straining to listen. At first there was nothing but the wind singing in his ears. Then he heard a faint sound carried on the breeze. Deep in his reflections, he had not heard it before.

They both stood, as if turned to stone.

It came again. A snatch of guttural conversation.

‘The Arabs,’ said Valens.

Chapter 17

CHAPTER 17

Adiabene