Maximius sensed the ironic tone straight away and dismissed Tullius with a curt word of command. As soon as there was no one near enough to overhear their conversation he turned back to Macro.

'What exactly were you and Tullius talking about?'

'Like he said, sir, it was a professional disagreement.'

'I see.' Maximius stared hard at Macro and chewed on his bottom lip. 'Nothing to do with that traitor we're looking for, then?'

Macro felt his pulse quicken and prayed that there was no sign of guilt written into the expression on his face as he replied, 'No, sir.'

'We're not getting very far with that line of inquiry, are we, Macro?'

'We, sir?'

'Of course.' Maximius glanced round suspiciously and then lowered his voice so that it was barely more than a whisper. 'Who else can I trust in this matter, Macro? Tullius is an old woman. Felix and Antonius are too young to be trusted with secrets, and uncovering secrets. You're the only one of my officers I can rely on. I want this traitor identified and brought to me in chains. You're the perfect man for the job, Macro.'

'Yes, sir.' Macro nodded. 'What exactly do you want me to do?'

'Just talk to the men. Nice and easy. Don't push for information. Say as much as you need to, nothing more, and just listen. Then report back to me.'

'Yes, sir.'

'Right then.' Maximius turned round and nodded towards the last patrol standing at ease by the gate. 'I want you to take them out today. The guide says there's a few small farms to the east. They might be worth checking out. After all, Cato's lot will need food. If there's any sign that the locals have been harbouring them, you know what to do. Make an example of them.'

'Yes, sir.'

'The optio there, Cordus, is from Felix's century. He's a good man, you can rely on him. Now you understand your orders?'

'Yes, sir.'

The cohort commander paused a moment to look intently at Macro. 'Report everything to me when you return – everything.'

Macro saluted. 'I understand, sir.'

'Good luck, then.'

At noon Macro gave the order for the patrol to halt. Sentries were posted at each end of the track and the rest of the men gratefully slumped down on to the ground and reached for their canteens. The sky was a piercing blue, except for a scattering of puffy clouds drifting slowly away to the south of the marsh. Macro craved some shadow and looked at them longingly. The sunshine beat down on the still air that hung over the marshland and every man in the patrol was sweating heavily. The felt liner inside his helmet was drenched and Macro could feel beads of sweat running down his forehead, and dripping on to his cheeks. The heat was exhausting and the men had grumbled about their lot all morning, until Macro had lost his patience and ordered them to shut up. Thereafter they had marched along in silence, growing steadily more surly as the guide led them along the narrow winding paths, through rank-smelling shallows and thickets of gorse without encountering any sign of habitation.

'Cordus!' Macro waved him over. 'Ask him how much further we have to go.'

The optio nodded and strolled over to the native guide. He was a short man, thickset and clad in a rough woollen tunic and leggings. He was barefoot, and bare-headed and the length of leather tied loosely as a collar had chafed his skin and left a weeping red welt around his fat neck. The guide was a metalsmith and depended for his livelihood on the strength in his arms, not his legs, and had suffered even more than the armour-clad legionaries from the morning's march. Although he had claimed to know the route to the farms scattered amid the marsh, Macro suspected that he had nearly lost the way on several occasions. The fact that his family were held hostage in a small cage in the Roman camp had been more than an adequate incentive for him to find the right trail again as speedily as possible. But now he looked spent, squatting on the ground, chest heaving for breath and looking longingly at the canteen his Roman guard was drinking from.

The man started with a small cry of alarm as Cordus poked him with the tip of his boot. With a cringe he looked over his shoulder, squinting up at the optio as Cordus gave a little jerk of the man's lead and forced him to struggle to his feet.

Cordus spoke to him in the smattering of Celtic he had picked up in Camulodunum while the Second Legion had been quartered there the previous winter. Between Cordus' accent and the native's unfamiliarity with the dialect it took a while for the question to be understood, and then the guide was pointing down the track and gabbling away in his own tongue until Cordus snapped irritably at him, yanking the leather lead to cut off the man's anxious stream of speech. He let the Briton drop down on to the ground and tossed the leash back to the legionary in charge of the guide before turning round and heading back to Macro.

'Well?'

'He reckons we should be there within the hour, sir.'

'Shit…' Macro mopped his brow as he tried to work out the timing. An hour there, say two hours looking over the small cluster of farms and then six hours' march back to the fort. It would be dusk before they made it back – if they were lucky. Blundering about in the marsh after dark was a pretty dire prospect. Macro took a quick swig from his canteen and wearily rose to his feet.'Get 'em up, Optio! We're on the move again.'

There was a chorus of groans and angry muttering from all sides.

'Shut your fuckin' mouths!' Cordus shouted, 'or I will personally kick your teeth out the back of your arses! Up! Up!'

Macro made a mental note of approval as the optio strode up and down the path, lashing out at any man who was slow to stir. Cordus was exactly the kind of optio Macro approved of. Not perhaps as bright as Cato had been, but a firm advocate of the kind of harsh discipline that pushed the men on. The thought of Cato was an unwelcome reminder of the purpose of the patrol. Macro compressed his lips and unconsciously started drumming the tip of his vine cane on the hard earth of the path. If they did find Cato and the others, what then? The orders were to take them alive, if possible. But alive they posed a threat to Macro. He would not put it past some of those legionaries to try to strike a deal to reveal the name of the man who set them free in exchange for a more lenient sentence. Some bloody fool was bound to try it on, and the moment Maximius was aware that such a deal was on offer he'd either agree and then, renege on the deal later, or bring in the torturers and get the information out of the hapless prisoner one way or another.

On the other hand, if Macro gave the orders to have them disposed of here in the marsh, questions would be asked. And it wouldn't take a genius to guess at the reasons behind his desire to have them silenced quickly.

Besides, Macro was not sure that he cared to have Cato and Figulus killed if they fell into his hands. It was a wretched situation in every way and he had yet to carry out the subtle orders Maximius had issued him with before he set out.

As the patrol continued along the path behind the overweight guide Macro fell into step beside Cordus.

'Hot work.'

The optio raised his eyebrows. 'Er, yes, sir.'

'Could do with a swim when we get back,' Macro said thoughtfully, as his subordinate tried to work out if this was a statement or an invitation.

'A swim, sir. Right… that's just what we all need.'

Macro nodded.'Especially after a day beating a path through this shitty marsh. If we ever find those bastards, I'll make 'em regret the day they ever decided to go on the run.'

'Yes, sir.' Cordus spat on the ground to clear his throat. 'Them, and that bastard who helped 'em escape in the first place.'

Macro glanced at him quickly. 'Whoever he is.'