Septimus glanced up at him. 'I'm sorry to say your fighting days are over.'

'Tell me something I don't know,' Castor hissed.

Septimus smiled briefly. 'I have to stop this bleeding. Give me your scarf, sir.'

Castor loosened the cloth, unwound it and passed it down. Septimus held one end behind the calf and then glanced up. 'This is going to hurt. Ready?'

'Just get on with it.'

Septimus wound the cloth round the leg, over the wound, and then bound it tightly over the ankle and tied it off. The searing pain was like nothing Castor had ever endured before and despite the cold of the night he was sweating freely by the time Septimus finished the knot and rose to his feet.

'You'll have to prop me up on the stairs when the time comes to make our last stand.'

Septimus nodded. 'I'll see to it, sir.'

The officers stared at each other for a moment as they considered the full import of their last exchange. Now that they had accepted the inevitable Castor felt that the burden of anxiety over the fate of his command had lifted. Despite the torment of his wound, there was a calm sense of resignation in his heart, and a determination to go down fighting. Septimus glanced away, through the door, and saw the enemy standing in clusters about the site, out of range of the rocks and stones that the auxiliaries had thrown from the watchtower.

'Wonder what they'll do next?' he mused. 'Starve us out?'

Castor shook his head. He had served in the region long enough in the east to know the nature of Rome's old enemy. 'They'll not wait for that. There's no honour in it.'

'What then?'

Castor shrugged. 'We'll know soon enough.'

There was a moment's silence before Septimus turned away from the entrance. 'So what is this? A raid? The opening of a new campaign against Rome?'

'Does it matter?'

'I want to know the reason for my death.'

Castor pursed his lips and considered the situation. 'It could be a raid. Maybe they saw the construction of this fort as an act of provocation. But it's equally possible they want to clear a path across the Euphrates for their army to cross. It could be the first move towards taking control of Palmyra.'

Castor's thoughts were interrupted by a shout from outside.

'Romans! Hear me!' a voice called out in Greek. 'Parthia calls on you to lay down your arms and surrender!'

'Bollocks!' Septimus snorted.

The man outside in the dark did not respond to the taunt and continued in an even tone. 'My commander calls on you to surrender. If you lay down your weapons, you will be spared. He gives his word.'

'Spared?' Castor repeated softly before he shouted out his reply. 'You will spare us and permit us to return to Palmyra?'

There was a short pause before the voice continued. 'Your lives will be spared, but you will be taken prisoner.'

'Slaves is what we'll be,' Septimus growled and spat on the floor. 'I'll not die a fucking slave.' He turned to Castor. 'Sir? What should we do?'

'Tell him to go to Hades.'

Septimus smiled thinly, his teeth luminous in the moonlight. He turned to the entrance and shouted his reply. 'If you want our weapons, come and get them!'

Castor chuckled. 'Hardly original, but a nice touch.'

The officers exchanged a grin and the other men smiled nervously, until the voice called to them one last time.

'So be it. Then this place will be your grave. Or rather… your pyre.'

A faint glow had appeared on the far side of the construction site and as Septimus watched a small flame flared up, silhouetting the warrior crouched over his tinder box.The flame was efficiently fed so that it quickly flared up into a small blaze as men gathered round to light torches hastily gathered from the surrounding scrub. Then they approached the watchtower and as Septimus watched the first of the fire arrows was offered to a torch until the oiled rags caught alight. At once the archer drew his bow and shot at the watchtower. The arrow blazed through the darkness and thudded into the scaffolding, scattering a small shower of sparks. Immediately, other arrows flamed towards the structure, embedding themselves in the wood with splintering cracks and burning as they lodged there.

'Shit!' Septimus clenched his fist round the handle of his sword. 'They mean to burn us out.'

Castor knew there was no water in the tower and he shook his head.'There's nothing we can do about it. Call the men down from the watchtower.'

'Yes, sir.'

A short while later, as the last of the survivors crowded into the small guard room at the foot of the tower, Castor hauled himself up and leaned against the wall so that he could address them.

'It's all over for us, lads. We stay here and burn, or go out there and take some of those bastards with us. That's it. So when I give the order, you follow Centurion Septimus out of the tower. Stay close to each other and run hard at them. Understand?'

A handful of them nodded and some managed a few words of acknowledgement. Septimus cleared his throat. 'What about you, sir? You can't come with us.'

'I know. I'll stay here and deal with the standard. They can't be allowed to take that.' Castor held his hand out to the cohort's signifer. 'Here, let me have it.'

The standard-bearer hesitated a moment, and then stepped forward and handed the shaft over to his commander. 'Take care of it, sir.'

Castor nodded as he grasped the standard firmly and used it to support the weight on his injured leg. Around them the crackle and soft roar of flames filled the warm air and a lurid orange glow lit up the ground around the watchtower. Castor staggered towards the narrow wooden staircase in the corner. 'When I get to the roof, I'll give the order to charge. Make every thrust of your spears and every blow of your swords count, lads.'

'We will, sir,' Septimus replied softly.

Castor nodded and clasped the centurion's arm briefly, and then, gritting his teeth, he made for the roof, painfully working his way up the wooden stairs as the air grew heated around him and wisps of smoke curled into the orange light seeping through the windows and arrow slits. By the time he reached the roof, the side of the watchtower closest to the enemy was ablaze. Castor could see scores of Parthians waiting in the bright glare of the flames and he drew a deep breath.

'Centurion Septimus! Now! Charge!'

There was a thin chorus of war cries from the base of the tower and Castor saw the Parthians raise their bows, concentrating their aim, and then the air was filled with the flitting dark splinters of their arrows. Over the parapet he saw the small compact body of his men charging out across the site. Their shoulders were hunched down behind their shields as they ran straight at the enemy, following Septimus as he bellowed insults at the Parthians. The archers stood their ground and shot their arrows as fast as they could at the moving target. Those who still had fire arrows to hand loosed those and brilliant flaring paths cut through the air towards the auxiliaries. Several lodged in shields and burned there as their owners ran on. Then Castor saw Septimus suddenly draw up and stand still, his sword dropping from his hand as he clutched at the point of an arrow that had passed through his neck as the last of his cries still echoed over the site. Then he slumped to his knees and toppled forward on to the ground, writhing feebly as he bled to death.

The auxiliaries closed round his body and raised their shields. Castor watched them in bitter frustration. The impetus of the charge had died with Septimus and now they were picked off one by one as Parthian arrows found their way in between the shields and pierced the flesh of the men behind. Castor did not wait to see the end. Leaning heavily on the standard he crossed to the far side of the platform and looked down the cliff towards the river. Far below the mist had cleared and moonlight rippled off the swirling current as it flowed over some rocks. Castor tipped his head back and looked into the serene depths of the heavens and breathed the night air deep into his lungs.