Navigator

Perhaps this black powder will provide the potency they always lacked.'

Thomas looked pale. 'If it can be made to work – but what a horrible vision of destruction! What man is this Weaver to scatter the seeds of such carnage in our age?'

Roger Bacon seemed to care nothing for that. Saladin saw he was fired only by his curiosity, by the scent of fresh knowledge in his nostrils. 'You must retrieve these designs,' he said rapidly. 'And you must bring them to me. What you need to make all this work is a dominus experimentorum. Such as myself, or an assistant. I can see it now. A scheme of work designed around two elevating principles. First, the verification of the designs, and the physical principles on which they have been based, perhaps principles hitherto unknown to mankind and therefore an everlasting gift to scholarship. Second, the use to which the new understanding may be put, which is the protection of Christendom, and thereby the spiritual welfare of all mankind and the greater glory of God.'

Thomas said, 'You would think, brother, from what you say, that you were being asked to make cathedrals, not weapons.'

'There is no sin in using the power of the mind to build weapons to fight a just war. Why, your Weaver must be a Christian, or he would not have put these engines into the hands of Christians. How can this not be God's work?'

'I know very little about the Weaver, and you know less,' Thomas said sternly. 'You must ensure you discuss this work with your confessor, brother. Fully and regularly.'

'Yes, yes.' Bacon leaned towards Joan, eyes bright, like the cat's into which he had spent long hours staring, Saladin thought. 'Bring me your plans, lady. By God's bones, there is no other way – indeed it must be divine providence that brought you to me.

'Give me your plans,' said Roger Bacon, 'and I will build the Engines of God for you.'

XXIII AD 1248

The guard brought the two of them to Ibrahim's office: the accuser, a middle-aged man, and the accused, a scared-looking girl with a baby in her arms.

Ibn Shaprut sat silently at Ibrahim's side, plucking at his shabby robes. The doctor was a big man who had been a lot bigger before this dreadful summer of siege. Now his grimy, much-patched clothes didn't fit him properly, and Ibrahim sometimes thought his very skin hung loose, drained of fat. However Ibrahim was glad of his steady company and hard-headed advice.

It was an August afternoon in Seville, a city under siege and hot as a furnace. Distantly the muezzins called for prayer. Ibrahim was too busy for prayers. He tried to concentrate on the case.

The accuser was a man called Ali Gurdu. Aged about fifty, his face round as the moon, he looked sleek and prosperous in the middle of a famine that even reached inside the emir's palace, though in August's heat sweat stained his turban a grimy yellow. This man looked suspiciously at Ibn Shaprut. 'Who's he? A lawyer, a magistrate?'

'I'm a doctor,' said Ibn Shaprut.

'What's a doctor got to do with it? This is a case of theft, pure and simple.'

'I rely on his judgement,' said Ibrahim, 'so you will be respectful, Ali Gurdu.'

Ibn Shaprut was watching the girl. 'Your baby is very quiet.'

She smiled thinly. 'He's clever. He's learned not to waste energy crying.' Her voice was scratchy, like an old woman's. Her robe was filthy and torn, her eyes huge in a shrunken face, and the baby in her arms was wrapped in rags. She was called Obona. Ibrahim had had to confirm her age, which was sixteen; he had learned that hunger made you look young, even giving some a kind of ethereal beauty, before it turned you very old indeed.

'You brought him here today,' said Ibn Shaprut. 'You have no family who could have taken him?'

'My parents fled to Granada before the Christian armies came to the walls.'

'Without you?'

'They were ashamed of me. My grandmother stayed, though, and helped me. But she died in the spring.'

'Now you're alone,' said Ibrahim.

'Yes, sir.'

Ali Gurdu clenched a podgy fist. 'You'll be offering her a sugared apricot next. Enough of these questions! She's a thief! That's what this is all about, never mind her baby and her grandmother. She stole from me!'

Ibrahim glanced at his notes. Ali Gurdu described himself as a food merchant. He was steadily selling off a hoard of dried fruit and salted meat and rice. That wasn't quite against the law, even at the exorbitant prices he no doubt charged. But Ibrahim thought there was a stink about the man that was more than just a layer of greasy sweat.

'She came to you as a customer,' he said. 'She bought a bit of salted meat.'

'What meat was that?' Ibn Shaprut asked the girl.

She shrugged. 'Rat, I think. Or cat. What else is there?'

The flesh of a rat, which had no doubt gorged itself on the bodies in the communal graves. 'So you took your bit of rat-'

'She took two sticks,' Ali Gurdu insisted. 'More than she'd paid for.'

'One wasn't enough,' the girl said miserably. 'The baby – I still feed him.'

'That is draining for your body,' Ibn Shaprut said gently. 'I understand.'

'She ran away with the meat she stole.'

'But you didn't chase her,' Ibn Shaprut said. 'She was only caught because she was unlucky enough to run straight into one of Ibrahim's bailiffs. If not for that you'd have said nothing about it.'

Ali Gurdu blustered, 'I was simply slow about it. Shocked. Distressed! I'm not used to such blatant thievery, from a very young girl too. What's the world coming to?'

Ibrahim raised a hand to silence him. 'Obona, how did you pay for this meat? Do you have money?'

She shook her head. 'My parents took what we had. My grandmother had a few coins, but when she was dying I spent the last of those on a bit of water.'

'Yet you must eat,' Ibrahim said. 'Yet you must drink. How did you pay him?'

She glanced at Ali Gurdu, and looked down at her baby, clearly ashamed.

'Well, I think that's clear enough,' Ibrahim said, not bothering to hide his disgust. 'Food for sex, Ali Gurdu? Is that the game?'

Ali Gurdu looked defiant. 'You could call it pity. I mean, look at her. Skin and bone. Who would want her?' He slammed one fat fist into another. 'But it's still theft, that's the top and bottom of it. So what are you going to do about it, 'vizier to the vizier'?'

Ibrahim's thirst raged, though there were hours to endure before his next sip of his water ration. He felt fouled by this grubby case, like so many others he had had to deal with.

It was all the fault of the Christians. The Castilians had lain siege around the city in the spring, when King Fernando had assembled a fleet of ships from the coastal waters, forced his way up the Guadalquivir and rammed the pontoon bridge. Thus, after years of pressure, Fernando had at last bottled the city up. As spring gave way to the usual ferocious summer, disease, famine, and worst of all drought had afflicted the city. Fernando seemed content to wait it out, even as his own men dropped of drought and fever. Once there had been rumours of a relieving force coming from Granada. But that taifa's ruler Muhammad Abu Alahmar, concerned above all to secure his own position, submitted to King Fernando and actually joined in the siege against his fellow Muslims in Seville.

Sometimes Ibrahim wondered grimly how it would be if the siege never lifted. Would Ibrahim and those like him be forced to administer the death of an entire city, down to the last man, the last child, the last dog and cat?

But meanwhile, today, he had Ali Gurdu and this child-mother Obona to deal with. He glanced at Ibn Shaprut's stern face, seeking guidance.

'Here is my decision. Ali Gurdu, you have a certain usefulness. Men like you, with your grafting and your