'Carry on.'

As the meagre measures of water were poured into the proffered canteens Macro beckoned to Cato and began to walk away from the line of men.When they were safely out of earshot he stopped and faced his friend with a fierce expression.

'What the hell was that about?'

'Discipline, sir.'

'You can drop the "sir" routine when the men aren't listening, Cato.'

'All right then.' Cato nodded. 'I can't understand you. When did you ever let a man get away with something like that? If we were back in camp you'd have Tadius digging shit out of latrines for the rest of his life.'

'I might,' Macro conceded.'But we're not in camp.We're about as far out on a limb as we can be.There's enough bad feeling between your lads and mine already without fanning the flames any further.'

'Your lads and mine?' Cato repeated. 'You make it sound as if we're not on the same side.'

'That's the point. If these men see themselves as enemies then we're in deep trouble the moment any real foes turn up. Petty grievances are a luxury we can't afford.'

'And what about discipline?'

'Sometimes you have to compromise. Anyway, you've taken care of the discipline, it would seem.' Macro sighed. 'If a day without water doesn't kill Tadius, then you will have made yourself an enemy for life. Congratulations.'

Cato was about to reply when there was a shout from the camp. 'Cavalry patrol coming in!'

Macro shook his head wearily. 'Will I get no bloody rest tonight? Come on, something's up.'

The sound of hooves drumming across the desert announced the return of one of Cato's cavalry patrols and the two officers hurried over to where the decurion and his men were reining in at the edge of the column's sleeping lines.

'Where's the prefect?' the decurion called out anxiously.

Cato raised a hand. 'Over here. What's happened?'

'Beg to report, we've sighted a large force of mounted men, sir.' The decurion was breathing heavily as he steadied his mount, still snorting for breath after its gallop back to the camp. 'To the south.'

'How far from here?' Macro snapped.

'No more than two miles, sir. Seemed to be heading towards us.'

'Could you identify them?'

'Too dark, sir. I watched long enough to gauge their heading, then came to report. I'm sure they didn't see us.'

Cato interrupted. 'Mounted men, you say? Horse or camel?'

The decurion paused for a moment. 'Bit of both, sir.'

'Then it's likely to be a force from Palmyra, rather than Parthians. Parthians are supposed to favour horses.' Cato glanced at Macro. 'According to my sources, sir.'

'Your sources?'

'What I read in the library at Antioch.'

'Then it's bound to be true,' Macro grumbled sarcastically. 'Right, we haven't time to get out of their way. So we'll have to lie low and keep quiet until they have passed.'

'And if they ride right up to us?' asked Cato.

'Then we give them the surprise of their bloody lives.'

Cato recalled the mounted patrols and sent the cavalry back down the track to hide in a small depression the column had marched through before halting for the night. If there was a fight the Romans could not risk confusing their cavalry with the approaching horsemen in the darkness.When they heard a bucina signal they were to rejoin the column. Meanwhile the auxiliary and legionary infantry put on their armour and drew their swords before lying down beside their shields. If it came to a fight, then this would be a confused affair at close quarters. Javelins would be too cumbersome, so the short sword favoured by the Roman army would settle the affair. The officers, crouching low, passed along their lines harshly whispering to their men the need to keep still and silent and not to move a muscle unless an order was given. Macro and Cato crept a short distance forward, in the direction of the approaching horsemen, and squatted down, straining their eyes as they scanned the almost featureless landscape to their front.

'If it is the enemy,' Macro said softly, 'we're only going to have one chance to hit them hard. If they can break away from us in good order, then the column's going to be arrow fodder come first light.'

'I know.'

'So if the moment comes, you and your men go in hard.'

'Trust me, Macro. I know my job.'

The older officer turned to his young friend and grinned. By the dim light of the stars his teeth seemed inordinately white in the muted dark shades of the night. He clapped Cato on the shoulder. 'Of course you know your job.You learned from the best.'

They both chuckled for a moment and Cato felt a little of the nervous tension drain from his body. If it did come to a fight, there was no man better to have at his side in a battle than Centurion Macro. Then he froze, squinting out across the desert.

'There!' He leaned closer so that Macro could follow the direction indicated and thrust his finger towards the horizon. At first Macro could see nothing. He blinked to clear his eyes and stared again.

'Can't see a thing. Are you sure?'

'Of course I am,' Cato responded irritably. 'Use your eyes.'

This time Macro saw them, or rather he saw the dark smudge emerging from the greater gloom no more than half a mile off. As the detail began to resolve he could even see the faint penumbra of sand kicked up by the horses' hooves. As the column approached something else occurred to Macro.

'They're quiet,' he whispered. 'They move like ghosts.'

For a moment, a chill gripped Macro's spine at the thought.There had certainly been enough blood spilt across this land for it to be haunted by hosts of the spirits of the dead.

'Relax. They're alive enough, for now,' Cato replied softly. 'They're quiet all right. The question is, what the hell are they doing out here? And why move after dark? They're not part of a caravan, that's for sure. Given the situation, they're almost certainly hostile.'

'How can we be sure?'

'We're the only Romans out here, and I'd have thought any friends we have are bottled up in the citadel at Palmyra. Besides…' A nasty thought struck him. 'It's almost as if they're looking for something. Us perhaps. In which case, I doubt they're friendly.'

'Us? How could they be looking for us? They can't possibly know we're here. Not yet.'

'Why not? Someone at Chalcis could easily have ridden ahead to raise the alarm.'

'Shit, you're right.' Macro ground his fist into the sand. Then he glanced at Cato.'If they're looking for us then why aren't there any scouts?'

Cato thought for a moment. 'Could be that they don't think we've advanced this far yet. Anyway.' Cato nudged him. 'They're coming our way. We have to get back to the column.'

The two officers rose into a low crouch and worked their way back to their men, taking care not to disturb too much sand and betray their presence. Macro stole back towards his legionaries as Cato lay down beside his standard-bearer, drew his sword and pulled his shield up beside his body. He glanced round and saw that his men were as flat to the ground as they could be and in the darkness there was every chance that they would be missed by the horsemen, provided the latter did not pass too close or, worse, stumble upon the concealed Romans. Cato's heart was beating like a hammer and his excited senses were overwhelmed by the sight, sound and smell of the cold desert night. For a moment there was nothing, and then the faintest sound of muffled hooves before the head of the column of horsemen was visible against the faintly lighter horizon.

One of his men muttered something close by and Cato swivelled his head round to glare in that direction, and let a faint sound escape through his clenched teeth. 'Shhh.' If he discovered who the man was later, he thought furiously, he'd have him beaten. If they both survived the night.