'Thus from Jerusalem to Rome Christendom is in retreat,' Grace said relentlessly. 'Only here in Spain are Christian armies taking the fight to the Muslims. Only here, under Isabel and Fernando, are Christians winning. And that,' she said, 'is the key to the future.'

Ferron considered. 'But the monarchs are barely at ease on their own thrones. Their marriage united the Christian kingdoms of Spain, but they must deal with over-mighty nobles, empty coffers, a mixed population of Christians, Jews and Muslims – and, of course, the great canker of Granada, whose emir has refused to pay his proper tribute for fifteen years. The final war against Islam?' He smiled, languid. 'Let's be rid of the Moors in Granada first and then we'll see.'

Grace said urgently, 'Friar Ferron, I accept what you say. But time is short.'

'Tell me what you mean.'

And she told him briefly of another prophecy: her family's legend of the Testament of Eadgyth. Of the mysterious, crucial figure known by his three titles, the Dove, the spawn of the spider, and the Christ-bearer. Of warring destinies, which must be resolved 'in the last days' – which might come as soon as the year 1500.

'We have two decades, then,' Ferron said drily. 'Not long to conclude a war that has lasted for eight hundred years! But why do you want this, lady?'

'This is my destiny. My family's destiny, as we have perceived it since the days of Joan of the Outremer.'

Ferron pursed his lips. 'And you are unmarried. No husband – no children.'

'My life has a single purpose, friar. As I said, that has been the case since I was twenty. What need have I of children when I have the Engines of God?'

James shared a glance with Ferron, one of the few times the two of them communicated. Even Ferron looked disturbed by her intensity.

But he steepled his fingers and pressed the tips against his lips. 'What first? We must discuss the provenance of your various prophecies. But it occurs to me that the time is so short that this Dove of yours, if he exists, must already have been born. The Holy Brotherhood is rather good at finding people. I'll pass this on; we will find your Dove, if he lives.'

A young monk came into the room and apologetically whispered in Ferron's ear.

Ferron stood. 'We will continue our business later. For now, please, join me. I asked you to delay our meeting until today because I thought that you, as guests in our city, would like to witness the first triumph of the Inquisition.'

Grace stood with polite eagerness. 'And what triumph is that?'

Ferron smiled. 'We call it the Act of Faith.'

Auto-da-fe.

That February day, the procession formed up before Seville's unfinished cathedral. At its head was a company of Dominicans, barefoot, with their heads covered by black and white cowls like Ferron's. They bore the banner of the Inquisition, a knotted cross flanked by the olive branch of peace and the sword of retribution. Behind the monks walked magistrates, then soldiers carrying wood for the fires.

And then came the condemned – seven of them, six men and a woman, flanked by soldiers bearing lances to ensure they could not escape. More hooded monks followed, chanting for repentance, and finally drummers who hammered out a heavy, doleful rhythm.

Ferron led Grace and James to join a gaggle of other notable citizens who trailed the drummers. They passed along narrow streets crowded with people who came to stare at the condemned. Some of them were foreigners, James thought, Portuguese explorers or Italian merchants, ambassadors from an entirely different world, who watched this gruesome parade with sneers of disgust – and yet they watched.

James himself was horribly fascinated by the faces of the condemned. They wore yellow gowns, carried candles, and had nooses around their necks. They were influential conversos – Jews converted to Christianity, or even the descendants of converts – whose treacherous reversion to Judaism had been rooted out, tried and sentenced. One young man looked frightened, and he continually crossed himself and mumbled prayers; if he was secretly Jewish he didn't look it now. The others merely looked stunned, or disbelieving.

The procession snaked out of the city walls to an open field. Here bare wooden stakes had been set up in a row, their purpose blunt and obvious. The condemned were tied to these stakes. One man struggled, another wept, and that younger man crossed himself until his arms were pinned. The rest bore the procedure in stoical silence.

Ferron pointed out one Dominican, a tall, pale figure with a flattened nose, like a boxer's. 'Torquemada,' he murmured. 'Your first contact, madam. Not yet an Inquisitor, actually, but his soul yearns for the good work. Ferociously pious and yet a master of organisation. Perhaps every cleansing needs a cool mind like his!'

The leader of the Dominicans stepped forward, and began to deliver a sermon in windy Spanish, laden with quotations from Revelation.

Ferron whispered to Grace, 'He is Friar Vincent Ojeda, of the Monastery of San Pablo. He led the commission which established the Inquisition in the first place, to root out weakness and treachery in our new state. For connoisseurs of apocalyptic preaching, his sermons are collectors' items,' he said. 'But this is a moment for which he has campaigned all his adult life.'

A portly, intense man, Ojeda was alight with joy in this killing place, James thought. And if James was watching Ojeda, so, he found, Ferron was watching him.

'I wonder what you are thinking, young brother. Your expression is complicated. Are you concerned that the innocent may be wrongly condemned? It is possible; we are human. But remember the words of the Pope's legate at the time of the Albigensian heresy: "Slay all. God will know His own."'

'That would be small comfort were I at the stake today.'

'True, but you aren't at the stake, are you? I've known your type before. You are too intelligent to be truly pious. What do you think of us? What do you think of me?'

James decided to answer honestly. 'I think you are a man of affairs,' he said. 'Of business. Of this world, more than the next. You see this Inquisition as a way for you to achieve your goals, and for your monarchs to build a strong and unified state.'

Ferron's head swivelled, sleek. He said to Grace, 'Your adviser has a mind of his own, I see.'

Grace sneered at James, effortlessly crushing him; he looked away. 'Unfortunately, yes,' she said. 'He's one of the brightest of his generation, so his abbot assured me. And he's an expert on the Engines of God. But he shows an unruly independence of thought.'

'Have you always been "unruly", boy?'

'My father is a farmer,' James admitted. 'We were not rich. As I grew he passed me into the care of the Franciscans. He said I was too intelligent to be of any use behind the plough.'

Ferron barked laughter. 'A sensible man. But I'd have strapped you to the damn plough and beaten the brains out of you. However you're not entirely wrong. One can unite one's fellows behind a holy banner. And we need uniting, we squabbling Christians, for we face our mortal enemy in Islam in Granada, and our own cities are full of Moors and Jews. We did not cleanse ourselves in the past, as you English did long ago. But once we have been purified by the Inquisition we will be in a position to conclude a Reconquest that has been stalled for far too long.'

When Ojeda was done thrilling the gathered mob, a notary stepped forward and read out the crimes of each penitent. One had engaged in Jewish rituals; one had mocked the Host which was the body of Christ; one had prepared his lamb meat in accordance with Jewish instruction; and so on. They had all confessed to this when 'put to the question'.