The man had his hands curled round them. His eyes were uncomprehending.
'You will be all right,' said Ballista. He ordered two of his equites singulares to carry the man to a dressing station. The guardsmen looked dubious at this fool's errand but obeyed anyway.
Back behind the parapet, Ballista steadied himself. He counted to twenty then peered out. There was the Persian ramp; there was the void between the ramp and the wall. But now the gap was less than five paces wide. From underneath the screens at the front, seemingly almost close enough for the defenders to touch, earth and rubble, the occasional tree trunk, fell into the drop.
It would be today. Even if he had not seen the Sassanid troops massing at the far end of the covered walkways he would have known that it would be today. The Persians had clearly decided not to wait for the ramp to touch the wall but to use some kind of boarding bridge. The race was on. One way or another it would be decided today.
Ballista looked round. The messenger's blood was already soaking into the brickwork, a film of dust dulling the bright-red pool. Ballista nodded to those with him and, again keeping very low, crawled to the trapdoor. Maximus, Demetrius and the three remaining equites singulares clattered down the stone stairs after him.
Castricius was waiting at the entrance to his mine. With no formalities, he told them to get ready.
Ballista had been dreading this moment. It had to come. It was inevitable. He had to do it. But he did not want to. Don't think, just act. 'Let's go.'
As they walked down into the northern mine the sunlight from the entrance soon gave out. They moved quietly, just them in the darkness. None of the oil lamps in the niches was alight. Before they entered, Castricius had checked that no one had hobnails in the soles of their boots. They had left their sword belts, armour, helmets – anything metal – above ground. A careless spark could bring on their greatest fear, a premature fire.
In the pitch-darkness they moved in single file. Castricius led the way, feeling his way with his right hand on the wall. Ballista followed, gripping the back of Castricius's tunic in his fist. Then came Maximus, then Demetrius.
The floor was uneven. Ballista's boot half-turned on a loose stone. He imagined twisting his ankle, breaking his leg, being trapped down here. He fought down a surge of panic. Keep going. Don't think, just act.
The walk defied time, defied logic. They had been walking for hours. They could have walked all the way across the plain to the Persian camp.
Something changed. Ballista could sense space opening all around him. Possibly it was the quality of sound. The echo of their footfalls came back more slowly. The air smelt strange. It brought to mind different things: a stable, a butcher's shop, a warship. But the air was less close than before.
Castricius stopped. Behind him, the others stopped. Carefully, very carefully, Castricius opened his shuttered lantern just a chink. The thin beam of light barely illuminated the far side of the cavern. He held up the lantern. The roof was lost in shadows. Bringing the lantern down again, he directed the light at the timbers which held up the roof. To Ballista's eye there seemed very few of them, and those there were impossibly slender.
'There are just enough to hold the roof,' said Castricius, as if reading the mind of his commander. 'The wood is good, well-seasoned, tinder-dry. I have coated the timbers in pitch.'
'Good,' said Ballista, feeling he had to say something.
Castricius directed the light downwards. Most of the floor of the cavern was ankle-deep in straw. Around the bases of the timbers were pigskins stuffed with pig fat. 'A few cooks may have a problem, but they will burn well.'
'Good,' said Ballista in a voice that sounded strained to himself.
'And here is the heart of the matter.' Castricius shone the light behind them. To the left of the mouth of the tunnel where they had entered there were three large bronze cauldrons raised on wooden blocks, straw heaped around them. A trail of straw ran from them back up the tunnel. 'I found some bitumen for the first cauldron. The others contain oil.'
'I see,' said Ballista.
'Is it good?'
'Very good.'
'The fuse leads two-thirds of the way out of the tunnel. When you are clear, call to me and, with your permission, I will light it.'
'You have my permission.'
'Then let's go.'
Back on the surface the sunlight was blinding. Tears ran from their eyes. Having got his breath back, Ballista called to Castricius to fire the mine. They stepped away from the entrance.
For some time nothing happened. Then they heard the sound of Castricius's boots dislodging stones as he ran. He shot out of the tunnel, bent double but running hard. He skidded to a halt, looked around and, blinking hard, walked over to the others.
'It is done. Now it is in the hands of the gods.'
They struggled back into their armour and sword belts and ran to the tower. Taking the steps two at a time, Ballista burst out on to the battlements. He dived behind the parapet and looked out.
Almost everything was as it had been before. Yet Ballista knew something was wrong. There was the void. There was the Persian ramp with the screens along its face. Further back, level with the base of the ramp, was the line of mantlets. Further back still were the Persian artillery emplacements. Ballista searched hard, but he could see no wisp of smoke escape from the ramp. There was no evidence of what should be happening. There was no sign of the conflagration that should be raging in the manmade cavern below, the terrible fire that should be burning through the props, bringing down the cavern roof and the whole ramp above it. Everything on the surface was completely still.
That was it: everything was completely still – no incoming artillery, no archery, no rubble being tipped into the void. It would be now: the assault would come any second now.
'Haddudad, get the men up on the wall. The reptiles are coming.' Even as he shouted to the mercenary captain, Ballista saw the screen at the front of the Persian ramp begin to tip up. Allfather, we are going to lose this race. So close – just a few minutes more was all we needed.
The screen was pulled horizontal. Ballista ducked back behind the crenellations. A volley of arrows like a swarm of hornets buzzed across the fighting top, snickering off the stone. A sentry howled. The arrow in his shoulder, he spun round, lost his footing and tumbled down the slope of the inner earth ramp, where he got in the way of some legionaries coming out of their dug-outs and beginning the climb.
The arrow storm stopped. Ballista quickly glanced out. The boarding bridge was being pushed towards him across the void. A vicious-looking spike stuck down from beneath its leading edge. Ballista looked back inside the town. The defenders were labouring up the inner glacis, Roman regulars, mercenaries and local levies combined: they would not make it in time.
The boarding bridge crashed down, its spike well over the parapet. Without thinking, Ballista grabbed it. The wood was warm and smooth under his right hand. He swung his legs up on to the bridge. His boots thumped hollowly as he landed. Side on, shield well out in front, he drew his sword. He heard Maximus's boots thump down just to his left, those of another defender beyond the Hibernian. The boarding bridge was not wide. If no one fell, three men might hold it – at least for a short time.
In front was a line of fierce, dark, bearded faces, mouths open, yelling hatred. Under a coating of dust were the bright colours of Sassanid surcoats and the shine of their armour. Their boots drummed on the boarding bridge.
The easterner hurled himself baying at Ballista, not even trying to use the long sword in his hand. He wanted to smash his shield into that of the northerner, simply drive the defender back and off the bridge.
Ballista let himself begin to be pushed backwards. He stepped away to the right with his rear foot – there was no railing to the bridge; his boot was far too near the edge – and brought his left foot back behind his right. The Persian's momentum drew him on. As Ballista's body turned, he brought his sword over and, palm down, he stabbed it into the easterner's collarbone. There was a momentary resistance from the mail coat, then the point slid in, cutting through the soft flesh, scraping down the bone.
As the first Sassanid fell, beside and behind Ballista, the next came on. Ballista dropped to one knee and swung the sword in a wide arc at the man's ankle. The Persian hastily dropped his shield to take the blow. Leaning over, off balance, the man had little chance. Ballista lunged forward and up, driving his shield into the man's chest,
