'Overwhelming. Like this cathedral.'

Abdul glanced around. 'I think it's all a bit tasteless myself. However the cathedral's not meant for me, is it? Come,' he said cheerfully. 'Let me show you what is said to be the finest Moorish monument in Christian Spain.'

It turned out he meant the old mosque's muezzin tower, called by Christians the Giralda, which still stood. There was a doorway to it from the cathedral interior, and Abdul led Geoffrey up a series of broad ramps. Geoffrey had been expecting a staircase, but Abdul said the ramps had been designed this way so that guards on horseback could climb the tower. The ascent was easy but long, and Geoffrey, not a young man, was wheezing when he reached the top.

Here, huddling in his cloak against the wind, Geoffrey looked out over the roof of the cathedral, crowded with buttresses and pinnacles. It was as if he stood on the back of some huge stone beast. The city beyond was a patchwork of patios and domes that looked very Moorish to his untrained eye. But when he looked to the west, across the busy river with its pontoon bridge, he made out the hateful pile of Triana.

Abdul followed his gaze. 'You may not be able to help her,' he murmured. 'Agnes Wooler. The Inquisition is nothing if not relentless.'

'I can try. I was present at the destruction of the engines, but Ferron has no reason to suspect I had any involvement in that catastrophe – indeed, I didn't, not directly. And I am a Franciscan, quite senior in the order; I have letters from the church authorities in England. Ferron cannot deny me access to her hearing. At least I may learn what Agnes is forced to say to her interrogators. Then we may be forewarned for the battle to come over Colon.'

The Moor studied him. 'I don't believe you have come all this way just for the lofty purposes of prophecies. I know you by now, Geoffrey Cotesford. You care for people more than for ideas. You are here to save Agnes, an English girl who has fallen into the hands of the Spanish Inquisition.'

Geoffrey felt his anger mount, as it had so often whenever he reflected on that dreadful day in Derbyshire when Diego Ferron had effectively kidnapped Agnes Wooler. 'England is not Spain. In England we have a common-law writ known as habeas corpus. It dates back centuries, to the day the barons tempered King John's powers with the Magna Carta. Ever since it has served to preserve individual liberty by testing the legality of detentions. If she had not been removed from England, Agnes Wooler would be protected by such traditions, such laws. But not here, not here! Not in this country poisoned by war, and by the fear of the other.'

Abdul laid a calming hand on his arm. 'I'm afraid you can be sure that the Inquisition will extract everything she knows from poor Agnes before they are done. As for us, your name will surely be protected, but mine may not. And if I am implicated, I won't be able to help you further with the matter of Colon.'

'You must think of yourself, then,' Geoffrey said.

Abdul shook his head. 'No. We serve a greater cause, you and I.'

'Yes, we do, by God – by Allah! Thank you, my friend. But it comes to something when my most robust ally, here in this most ardently Christian of cities, is a Moor!'

The morning was advancing, and Abdul suggested they descend and return to the city for lunch. Geoffrey glanced once more over the cathedral's sprawling bulk. Far below he glimpsed a patio with orange trees, a relic of the Moorish origins of this huge church, where a boy sat on a low wall plucking at a guitar, and a girl danced before him, her arms raised, her feet clattering on the ground, her movements sensuous despite the February cold. The music drifted up to him through the rustle of the wind, a liquid sound. But the boy's song sounded almost like a muezzin's wail. In this city the Moorish face was only ever poorly disguised by the Christian mask, Geoffrey thought.

He followed Abdul down the ramps, where once the hooves of horses had clattered.

The courtroom was a cold stone room in the bowels of the Triana, windowless, its walls smeared with lamp black. Guards stood by the door and at the back of the room. They were beefy soldiers of the Holy Brotherhood, the religious police of Fernando and Isabel.

The panel of inquisitors was led by Diego Ferron himself. Two more clerics sat at either side of him. A pile of papers and books of procedure cluttered the desk before them, and a clerk made continual notes. The Inquisition was nothing if not orderly.

The only observer here was Geoffrey Cotesford, who sat as bravely as he could on a hard wooden chair. The chair had been brought into the room especially for him; Diego Ferron had made it clear that he was not welcome here.

An immense and detailed crucifix hung from one wall. Geoffrey reluctantly studied the image of Christ, whose wounds gaped. He supposed that he was the only one in the room who was aware of the irony of that gruesome sculpture of a victim of torture, suspended in such a place as this.

At last Agnes was produced. She was half dragged into the room by two more heavy-set brothers. She was wearing a grimy, colourless shift, stained brown with old blood, and her hair was matted and filthy. The size of the two soldiers with her was absurd, Geoffrey thought; either of them could have broken her with a single blow. She looked dimly around, at Ferron and his colleagues, and at the crucified Christ. There was a smell of decay about her, of shit and piss and blood. But her shrunken face had an odd, unearthly beauty about it.

And then she turned and looked directly at Geoffrey, and her eyes widened.

Geoffrey forced himself to smile at her, and made a blessing with two fingers. How she must blame him for prising her out of her anchoress's seclusion!

She dropped her head.

Ferron watched this coldly. Then he nodded to the brothers. 'Release her.'

The brothers let go of the girl's arms. She slumped to her hands and knees, and Geoffrey saw her back for the first time. Bloody stripes were clearly visible through the thin cloth of her shift.

Geoffrey found himself on his feet. 'This is an outrage. She has been whipped!'

Ferron turned that stern glare on him. 'All due and lawful process has been followed. The girl was given thirty days' grace in which to make her full and voluntary confession. When the thirty days expired, she was encouraged further to speak.'

'You call this encouragement?'

'And when she still failed to speak, she has been brought before the court. Perhaps she will speak here. But you, friar, will keep your silence, or you will be ejected.'

Geoffrey sat, fuming.

Ferron fixed the girl with his cold judgemental stare. 'Agnes Wooler. You are guilty of wanton destruction. You have damaged an ancient project with holy and pious purposes: you have blunted the swords of our new crusade. And, further, you took many lives in the process.'

Geoffrey put in, 'No. No lives were lost. She gave the friars in that manufactory sufficient warning. Whatever you think of her actions against the engines, she's not guilty of murder.'

Ferron ignored him again. 'Further I put it to you, Agnes Wooler, that you have been complicit in the corruption of a supplicant at the court of Fernando and Isabel, whom God has chosen as His emissaries on earth in this dark time. I mean Cristobal Colon, the navigator.' And Ferron spoke evenly about the 'Chinese' body discovered on the shore at Palos. Colon had believed this to be a relic washed east from Asia. But the body had been examined by a physician, who argued from blood-pooling that its tattoos had been applied after death. Its strange eye-folds were artificial too, the result of a bit of surgery, again performed after death. 'The body was a fake, designed to baffle Cristobal Colon and to thwart the holy purpose of the monarchs.'