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.’