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up with it. That or starve. It wasn't easy for me when we first came here to England – how long ago?'

'Three years already.'

'I needed the work. My mother and I had no money left. But I had no close family, nowhere to go.'

'And a face that didn't fit.'

'Yes. I'm grateful to you for finding me that first bit of employment with Umfraville.' A lord with extensive holdings here in the north country, who had made himself rich from a king's commission to protect the main droving routes to the north from the marauding Scots. The Umfravilles' castle at Harbottle on the Coquet was grand. But Saladin didn't have the stomach for the subdued, spiteful, slow-burning sort of war that consumed this border country – subdued but unending, for the nobles who waged it on both sides of the border grew rich from it. He had been glad to move to the pettier house of Percival.

Happy? Happiness was irrelevant in this life, he thought. Content? Yes, perhaps that was the word. Percival was a man of no brain, it seemed to Saladin, and too drunken to formulate any serious ambition. He was happy just to take his villagers' tithe and piss it away into the soak-holes behind his hall. But Saladin had no desire to risk his life supporting the petty ambitions of a more restless lord.

'This will suit me for now,' Saladin said. 'Until something better shows up.' He eyed Thomas. 'But my mother isn't so content, is she?'

'I'm afraid not.'

'I send her my money, you know. Just about all of it, keeping only a little for myself to buy a bit of pepper in Newcastle. I have few needs here; I eat with the lord, sleep in his house, ride his horses. What use is money?'

'She'd be lost without your contribution.'

'You wouldn't let her starve,' Saladin said.

'Well, true. We remember our benefactors. But she's a proud woman, Saladin. She doesn't want charity from a 'gaggle of monks', as she calls us.' Thomas sighed. 'But she has ambition enough for a hundred English lords.'

'Jerusalem remains in Saracen hands.'

'So it does. But things have changed, Saladin. You and your mother arrived here without wealth, but with one treasure.'

Saladin said reluctantly, 'Robert's cipher.'

'Yes. Perhaps you remember I found a scholar to study it – another Franciscan, a man called Roger Bacon. Remarkable chap. It's taken him some time-'

'Let me guess. He's worked it out.'

'So he claims. We'll have to judge his results.'

'We?'

'Your mother wants you with her, Saladin. In London, when the truth of the Incendium Dei code is revealed.'

Saladin said, 'I always hated that old nonsense about prophecies and codes, Thomas. Maybe it made our family rich in the past. But it never helped us in the Outremer, or since we have come to England. And I never thought it was real.' He waved a hand. 'Not compared to this. Land, toil, iron, blood, war – that's the real stuff of life. But my mother wants me with her in case this cracked code reveals secrets that will revive our fortune, and fulfil her life.'

'Yes. And I want you with her,' Thomas said severely, 'in the much more likely case that it does not.'

Mulling over Thomas's words, Saladin led him back to the manse.

XIX

Ibrahim and Peter slipped out of Seville.

They came to a hole in the ground just beyond the city walls. It looked like the outlet of a broken sewer or drain. Peter said, 'This is older than the Moorish city – Roman, we think, part of their sewage system. Of course the settlement here was a lot smaller then. The main Roman town, Italica, was some distance away. It's a bit mucky down here-'

'Just get on with it.'

The hole in the ground turned out to be a shaft, deeper than Ibrahim was tall, down which he had to drop. He found himself in a stone-clad tunnel, too low for him to stand up straight. He could see no further than a few paces. There was a smell of damp and rot, but nothing foetid; the sewer was long disused.

Peter used a flint to light a candle. His eyes were pits of shadow. 'Are you all right? Not everybody is fond of the dark.'

Ibrahim took a deep breath. 'I have no love of being buried alive. But it's my mother I'm more frightened of.'

Peter laughed, and clapped him on the back. 'Come. Let's face our nightmares.'

It turned out to be only a short walk, though a clumsy and difficult one, through the low tunnel. Ibrahim stumbled over a broken Roman tile. Then the tunnel opened out, and Ibrahim found himself walking into a big boxy room. Steps cut into the earth led down to a floor some distance beneath him. The walls were stone-clad, the ceiling timbered, and lamps glimmered in alcoves.

And in this chamber, deep underground, machines brooded, dimly glimpsed. There was a great tube mounted on a carriage. An upright wheel turned, a treadmill, with a man inside it to work it. What looked like the skeletal form of a great bird's wing gleamed and creaked. Scholars and artisans moved among these creations, murmuring quietly.

Ibrahim felt deeply uneasy, as if he had descended into a sorcerer's pit.

Peter led him briskly forward. 'This was some kind of water tank,' he said in a murmur to match the subdued voices around them. 'Always built big, those Romans, even when it came to their plumbing!'

'I never knew this place was here.'

'Not many do. It's on no plans; I dare say your emirate doesn't know it exists. When we needed a place to work in secret your mother, ever resourceful, started asking around among the criminal element.'

'Criminal?'

'Smugglers. Hoarders. Even bandits. They knew of this hole in the ground. It wasn't hard to take it over, clean it up, extend it a little…'

'Ah, the vizier's advisor. How good of you to make time in your busy schedule to visit your mother.'

Ibrahim had not seen his mother for four years. Subh wore a robe, white and pristine despite the dirt, and her hair was piled elaborately on her head, jet black. Unlike Peter she showed not a trace of the passage of time; she was as upright, powerful and magnificent as ever. Peter seemed to cower before her; he was as much in her thrall as ever.

Ibrahim bent forward to embrace his Mother.

But she subtly moved back and offered her hand, cold, the palm oily. 'Let's keep things formal,' she said. She showed not a trace of emotion.

'Mother, you haven't changed.'

'And what of you?' she asked. 'You're clean enough. A smart costume. And well fed, it seems to me.'

'I take only my ration,' he said stiffly, and it was true, though there were many in the palace who did not.

She prodded his belly. 'In that case you're not getting enough exercise.'

'What are you doing here, Mother?'

'You know very well. Building the war engines that might save Seville. Walk with me. See what we have made…'

She showed him her marvels. Here was a metal tube that used compressed steam to spit iron balls. Peter called it the 'thunder-mouth', for the great roar it would make when it was fired. Around the perimeter of the treadmill he had noticed was a series of crossbows. An archer sat at the axle, and as the wheel turned one bow after another was brought before him.

'The archer only has to aim and fire,' Peter explained. 'See, the ingenuity is that the mechanisms of the