thoughts moved along unconsidered back roads to the question of treachery. Demetrius had not been able to unravel its secrets, but the mere existence of the coded message attached to the arrow showed that there was still at least one traitor in the city of Aretc – or, at least that the Persians thought there was still a traitor active in the town. Ballista was sure they were right.
What did he know about the traitor? Almost certainly, he had murdered Scribonius Mucianus. He had burnt the artillery magazine. He had tried to organize the burning of the granaries. He was in communication, albeit sometimes interrupted, with the Sassanids. Clearly the traitor wanted the city to fall. Who could want such a thing, such a very monstrous thing? Could it be one of the townsmen, one of those who had lost their homes, family tombs, temples, slaves and all the liberties that were most precious to them because of the defensive measures Ballista had put in place? And hadn't he played his own part? How far could one go before destroying the very thing one was trying to protect?
If it was one of the townsmen, it was a rich one. Naptha cost a lot of money; it stank: only the rich could afford it, and the luxury of space to conceal its noxious smell. If the traitor was a townsman, it had to be one of the elite, one of the caravan protectors – Anamu, Ogelos, even Iarhai – or one of the other town councillors, like that ever-smiling Christian Theodotus.
But was it a townsman? What of the military? Ballista was very aware that Maximus still mistrusted Turpio. Not without reason. The humorous-faced Turpio had a past of proven duplicity. He had done well out of the death of his commander, Scribonius Mucianus. Despite Maximus's urgings, Ballista had never pressed the matter of what it was that Scribonius had used to blackmail Turpio. Maybe he would say one day, but Ballista very much doubted that Turpio could be forced to tell. On the other hand, Turpio had done well throughout the siege. His raid into the heart of the Persian camp had called for exceptional courage: one might say that he had earned the right to be trusted. But yet again, as Maximus had reminded him, courage is useful for a traitor – and so is being trusted.
Then there was Acilius Glabrio. Ballista knew that he was prejudiced against him, extremely prejudiced against the tribunus laticlavius. The crimped hair and beard, the supercilious manner: the northerner disliked almost everything about him. He knew that the young patrician detested serving under a barbarian. If Turpio was the traitor, it would be for money or to prevent his ultimate exposure as the killer of Scribonius – so money again. But if Acilius Glabrio proved to be the traitor, it would be about dignitas, that untranslatable quality that gave a Roman patrician a reason to believe in his superiority, a reason to exist. Ballista wondered if serving under an eastern monarch would be better for the dignitas of a Roman patrician than the humiliation of obeying the orders of a northern barbarian. In a certain light, the easterner could be thought less of a barbarian than a savage from the northern forests like Ballista.
Although Castricius was now in charge of this mine, the watch was being maintained on the area of town where the arrow with the coded message had struck the unfortunate soldier – who had, of course, died a few days after the doctor had extracted the arrow. Four equites singulares, whom Ballista could ill spare, kept up a more or less discreet observation. So far it had yielded nothing of use. As was to be expected, both Acilius Glabrio and Turpio had been seen on their rounds. All three of the caravan protectors had properties in the area. The Christian church ofTheodotus had relocated there.
Castricius returned. Again he squatted down, and again they talked of timber and olive oil and pig fat, of distances and density and momentum.
'Thank you, Centurion, thank you very much.' At Ballista's words, Castricius swelled with pride. He stood up sharply, but he was too old a hand to crack his head on one of the beams. He saluted smartly.
Stepping outside was like stepping into an oven. The heat sucked the air out of Ballista's lungs. Everywhere were shifting clouds of dust. The northerner could taste it gritty in his mouth, feel it sifting down into his lungs. Like everyone else he had a persistent cough.
As they walked to the southern mine there was a cry from the wall of 'baby on the way.' Most of the party threw themselves to the ground; Ballista and Maximus remained on their feet. The others might interpret it as coolness in the face of danger, but the two men knew that this was not true. Both stared upwards, thinking that if the missile were heading their way, they might get just a glimpse of it and have a split second to hurl themselves out of the way.
With a terrible tearing sound the stone ripped through the air above their heads and with a roar plunged into an already ruined house. A further cloud of dust rolled out.
Mamurra was waiting at the entrance to the other mine, which was hard up against the southernmost tower of the desert wall.
'Dominus.' His face broke into a smile.
'Praefectus.' Ballista smiled back. They shook hands then kissed on the cheek, slapping each other on the back. They had grown to like each other. Mamurra knew that, as far as the Dux Ripae was concerned, his conscience was absolutely clear. Nothing that he had said or written about him was unfair or malicious. The big barbarian was a good man. You could rely on him to do the right thing.
Ballista looked with distaste at the entrance to the tunnel – the big, roughly worked beams, the uneven floor, the jagged rock walls, the precarious hang of the roof. He stepped inside. The darkness stretched away in front of him, half-lit here and there by an oil lamp in a niche. It was strangely quiet in this mine after the noise of the other one.
'How goes it?'
'Good, so far.' Mamurra leant against a beam. 'As I said we would, we have dug deep; under the wall, the external bank, and the ditch. We have taken the tunnel out to about five paces beyond the ditch. There we have dug a short crosswise listening gallery. I found some old bronze round shields in one of the temples. I have put them up against the wall and have men listening at them.'
'Did the priests object?'
'They were rather unenthusiastic. But then, there is a war on.'
Although a slave should never initiate a conversation with the free, Demetrius could not contain himself. 'You mean it works? I had always thought that it might be just a literary conceit of the ancient writers.'
Mamurra's grin grew wider. 'Yes, it is an old trick, but it works. They amplify sound well.'
'And have you heard anything?' Ballista asked.
'Oddly, no, nothing at all. I am reasonably sure that if they were tunnelling near by we would have heard their pickaxes.'
'That must be good news,' Demetrius said. 'Either there has been a cave-in and they have abandoned their mine or it has wandered far off course and they are nowhere near our wall.'
'Yes, those are two possibilities,' Mamurra looked thoughtful, 'but unfortunately there is a third.' He turned to Ballista. 'When you and Maximus told me where their tunnel started out there in the ravine, I assumed – I think that we all assumed – that its purpose was to undermine the foundations of our southernmost tower, collapse it so that no artillery from there could interfere with their siege ramp. Now I am not so sure. It may well be more dangerous than that. Maybe they intend to dig clean under our defences and let their troops come up behind our wall. If so, they are waiting for the ramp to be near completion before they excavate the last part of the tunnel so that they can attack from two places at once.'
The whole party was silent, imagining an inexhaustible flow of Sassanid warriors pouring across the siege ramp while another erupted from the ground; imagining the sheer impossibility of the task of trying to stem both at once.
Ballista patted Mamurra on the arm. 'You will hear them coming. You will catch them.'
'What then?' Demetrius volubly clutched at this comfort. 'Will you smoke them out, throw bees or scorpions into their tunnel, release a maddened bear?'
Mamurra laughed. 'Probably not. No, it will be the usual – nasty work in the dark with a short sword.'
The arrow was coming straight for his face. With a convulsive twist, Ballista jerked himself back into cover. The side of his helmet hit the crenellation, the cheek piece scraping along the rough stone. He felt a muscle pull in his back. He had no idea where the missile had gone, but it had been far too close. He exhaled noisily, trying to will his breathing back to normal. Behind him he heard a low sob.
Keeping low, on his hands and knees, Ballista scrambled to the man who had been hit. It was one of his messengers, the one from the Subura. The arrow had gone in by the collarbone. Only the feathers still stood out.
