‘That’s bad enough, but there’s something else.’ Lupus looked from side to side. ‘I don’t know, but I can’t help feeling that we’re being watched.’

‘Who by? We haven’t passed a single dwelling for hours. The last person we saw was that shepherd a few miles back.' Marcus recalled the solitary figure holding a staff who had watched them from the top of a small cliff. ‘And he ran off the moment he saw us.’

‘Yes,’ Lupus pondered. ‘I’ve been wondering about that. Why did he run?’

‘He was just nervous. A party of horsemen appears and he fears that they might be brigands. That’s why.’

‘Perhaps there’s something else to it.’

Marcus looked at him. ‘What are you saying?’

‘Perhaps he wasn’t a shepherd. Maybe he was a lookout.

‘And who would he be looking out for?’

‘People like us. Travellers. Easy prey for a band of brigands. Or worse, the rebels. Supposing that man was a lookout, and he’s reported us?’

Marcus glanced over his shoulder, down the road to the point where it turned back on itself and was lost in the trees. There was no sign of movement. He shrugged as he faced the front again. ‘If there was anything sinister about him, then I think we’d know about it by now.’

Lupus was silent for a moment. ‘I hope you’re right.’

Both boys fell silent again, but Marcus was starting to share his friend’s anxiety. A mile further on they cleared the treeline and the road climbed towards a narrow pass between two rocky peaks hidden by wreaths of cloud. Marcus breathed a sigh of relief at leaving the confines of the forest. On either side the ground was littered with stones and rocks and afforded little cover for an ambush. Up ahead, the men were talking again and Marcus felt encouraged by their return to the earlier easy conversation and exchange of jokes. Even Lupus seemed more relaxed. The road began to narrow and Marcus allowed his friend to pull a short distance ahead. He needed time to think.

Caesar’s comment the previous night was preying on his mind. Despite the debt that Caesar owed him for saving his niece’s life, it would mean very little if he decided that Marcus represented any threat to him, or to Rome. Marcus felt he was living on a knife-edge. He must be careful about every comment he made and keep the brand on his shoulder out of sight. He could trust no one, not even Lupus. A wave of bitter loneliness washed over him and he felt the first hot tears at the corner of his eyes. Marcus raised his hand and cuffed them away angrily. He could not afford to be weak, he told himself. He had to be strong if he was to survive. And he had to survive if he was to rescue his mother.

A cold speck brushed his cheek and he looked up and saw that it had begun to snow again, light flecks of white dropping gently from the overcast sky. Ahead, the road came to another hairpin bend, and Caesar and Festus steered their mounts round to lead the column up the new stretch. As Marcus came to the bend, some sixth sense caused him to rein his horse in, and he turned in his saddle to look back down the slope towards the forest.

He saw them at once. Another party of horsemen, twenty or so of them, no more than half a mile behind. They were moving at a slow trot and appeared in no hurry to catch up. Even so, Marcus felt a pang of concern and kicked his heels in as he urged his horse forward.

‘Make way!’ he warned Lupus, who glanced round with a surprised expression before steering his horse to the side of the road. Marcus trotted by without any comment and carried past the other riders until he drew up alongside Caesar.

‘Sir, there's someone following us.’ Marcus pointed down the slope, but the lower road was invisible from this point. Caesar glanced down the rock-strewn ground.

‘What are you talking about? I see no one.’

‘They are there, sir. I saw them plainly.’

‘How many?’ Festus asked sharply.

‘Twenty, about.’

‘Where?’

‘They were just coming out of the forest.’

‘Well, I can’t see much thanks to this snow,’ Caesar muttered. ‘Are you sure about this, Marcus?'

‘I am certain, master.’

Caesar stroked his chin. ‘You saw them from where exactly?’

‘Back where the road turns.’

Caesar sighed. ‘Then we'd better have a look.’

The column halted and the three made their way back down the line until they reached the bend and stopped as close to the edge as they dared to peer down the steep slope. Below, the snow was falling hard and it was difficult to make out more than the dim outline of the forest.

There was a brief silence before Festus growled, ‘I can’t see anything.

‘No,’ Caesar added quietly before he turned to Marcus. ‘Are you quite certain about what you saw? Tired eyes sometimes play tricks.’

Marcus felt a brief instant of doubt, then shook it off. ‘I saw horsemen, sir. I know it.’

‘Well, there’s nothing down there now,’ said Festus. ‘Nothing I can see.’

‘Nevertheless, I trust the boy’s judgement,' Caesar responded firmly. ‘I want you to stay at the rear. Keep watch behind us. If you see anything, then let me know at once,’

Festus bowed his head and Caesar was about to turn his horse round when the snow cleared and, as if a veil had been drawn back, the ground beneath came into view again, together with the party of horsemen trotting up the track, closer now than when Marcus had first spotted them.

‘Get the men moving!’ Caesar snapped. ‘Let’s get up to the pass. It’s a natural choke point. We can wait for them there. If they mean us no good, then that’s where we shall make a stand. Go.’

Festus wheeled his mount away and it kicked up a spray of snow as he galloped to the head of the column. Caesar squinted as he scrutinized the horsemen below. ‘They’re armed. I can see spears, shields, some helmets. Not soldiers from our side at any rate. There’s no standard at their head. No sign of an officer. I fear they may be trouble, young Marcus.’ He blinked and turned to look at his former slave. ‘Well spotted. Once more you serve me well. Come, I want you at my side.’

They trotted back to the head of the column and Caesar waved them forward as he kicked his heels in. There was no need to race ahead of the other men, and in any case the ground beneath the light layer of snow was frozen hard and presented an additional hazard to any horse and rider who slipped and fell. They continued up the slope, and at every corner Marcus looked down to see that the pursuers were remorselessly edging closer. They urged their mounts on, heedless of the risk, and he saw one or two of them tumble into the snow. One went over the edge and tumbled a good thirty feet before landing hard against a rock. The rider lay dazed and the horse floundered in a drift as it struggled to regain its feet. Then they were lost from sight again.

As the road approached the pass it began to level out and Caesar called to his men. ‘We’re almost there! As soon as we gain the pass, we’ll stop and dismount!’

Marcus was about to spur his beast on when he looked back and saw Lupus struggling to stay in the saddle, his face white and drawn with fear as he clung to the reins. Before Marcui could drop back to help him, Festus drew alongside the scribe and urged the boy on. He looked up and caught Marcus’s eyes, nodding as if to reassure him that he would take care of Lupus. Marcus leaned forward and kicked his heels in to catch up with Caesar. Ahead of them crags rose up on either side of the pass, dusted with snow and ice.

They were barely a hundred feet from the narrow opening to the pass when a tall figure stepped out from a rock and strode confidently into the middle of the road. He stood facing the riders, hands on hips.

‘What’s this?’ Caesar hissed as he slowed down and threw up his hand to stop his men ploughing into the back of him. The column slowed to a walk while Marcus’s gaze flickered from the man to the rocks on either side and back again. He felt the familiar tingle of apprehension in the hairs at the back of his neck.