Valens looked around for his sword. It was lost somewhere in the debris of battle. He snatched up a discarded Sassanid blade. Only when he reached his mount did he remember that it was injured. All the others in sight were dead or also grievously hurt. He turned and started to run.

Their tents were pitched away from the river at the north-west corner of the encampment, a little apart from those of the Heruli. Valens left the riverbank and cut into the heart of the camp.

The nomads had laid out their shelters in neat, ordered streets. They were well spaced so there was no danger of tripping over guy ropes or other impediments. Valens ran as fast as his tired legs would carry him. By the time he turned into the last thoroughfare, he was bathed in sweat, and the breath was beginning to burn in his lungs.

There were only serving women left in the camp. They stared, silent and round-eyed and wondering, as he raced past.

The thick quilted jacket and sword belt were getting in the way, slowing him down. Not stopping, he peeled off the jacket, unbuckled the belt, and left them lying in the dirt.

The Persian cavalry had been waiting when they came down from the Castle of Silence. Valens had been right. There was a traitor. He was after Prince Sasan. Why he wanted the boy, why he had betrayed his companions, Valens still could not imagine.

The man’s horse was cropping the grass off to one side.

The Greek slave girl was outside Sasan’s tent. Her throat had been cut. No attempt had been made to conceal her body. She had been cast aside as a thing of no importance.

Without stopping to think, Valens pulled back the hangings and burst through.

The interior of the tent was gloomy, wreathed in smoke.

Sasan was cowering amidst the baggage by the back wall.

Clemens was by the hearth in the centre of the tent. There was blood on his sword and his forearms.

As Valens entered, Clemens half turned, keeping an eye on the boy.

‘You should not have come,’ Clemens said.

‘Why?’

‘I have no wish to kill you.’

‘And Severus and Quintus, did you not want to kill them?’

‘No. It was necessary.’

‘We swore an oath. Why have you broken your word?’

‘Orders.’ Clemens smiled mirthlessly. The deep furrows on his face were like lines incised in marble. ‘We will do what is ordered, and at every command we will be ready.’

‘Whose orders?’ The longer Valens could keep Clemens talking, the better chance he could take him off guard.

‘You do not need to know.’

‘Why the boy?’

Clemens glanced at Sasan. ‘There are those in Rome who want a war with Persia, and there are those who do not. If this child lives, thousands will die: soldiers on the battlefield, women and other children in the sack of towns.’