At the head of the procession, walking slowly, was a black knot of prelates, somehow sinister in their darkness. And at the heart of this group, shining in a gown of bright colourful silks, was a tall, imposing woman, her features strong, her eyes chips of aquamarine. Her chestnut brown hair was tied back under a small, delicate turban, for when she entered a conquered town she had a custom of dressing respectfully, with a nod to the Moorish style.

It was the Queen, of course, Isabel of Castile. As she passed her soldiers cheered.

'Magnificent, isn't she?'

Diego Ferron had joined them. The Dominican friar, tall and wire-thin, wore a robe so black it seemed to suck the daylight out of the air.

With him was a Moor, a portly man of about fifty with an expressionless, weather-beaten face. He carried a sheaf of documents under one arm, and he waited, eyes empty, at Ferron's side.

Grace took Ferron's hand and kissed it. 'My good friar. You found me, I'm so glad.'

Ferron nodded. He glanced at James and made a curt sign of the cross to him with two upraised fingers. 'And I'm glad you are here at this moment of triumph, madam. Even now King Fernando is composing his letter of jubilation to the Pope, I'm told. Oh, I should introduce my mudejar.'

The Moor smiled. 'I am Abdul Ibn Ibrahim. By profession I am an astronomer. Today I serve the friar.' He said this without apparent bitterness.

Ferron said, 'Actually he is attached to the staff of the emir in Granada. The emir has sent a delegation to Ronda to witness the enactment of the treaty of capitulation. We do try to be civilised about these things. And so I am shadowed by this mudejar. Well, he is useful; his Latin is quite good.'

James introduced himself. 'And this is the lady Grace Bigod, of Buxton – we are from England.'

The Moor's eyes glinted. 'I know who you are.'

It was a remark that puzzled James. But Abdul said no more.

Ferron said, 'Ah, the Queen is nearing us…'

They applauded as Isabel with her retinue continued her progress down the road.

Ferron watched admiringly. 'I've met her several times. A remarkable mix of courage, piety, and sheer glamour! In her way, you know, she is as valuable to the cause of Christendom as ten thousand knights, for the men love her in a way they will never love Fernando, though they admire his cunning and leadership. And she is competent too. Since the fall of Ronda she has already rededicated the main mosque, and ordered cart-loads of sacred books and crosses to be shipped in from Cordoba and Seville, along with good Christian settlers to occupy the abandoned properties. Thus she has completed the city's conquest by her cleansing.'

James asked pointedly, 'And the Jews and conversos? Are they to be cleansed too?'

Ferron smiled thinly at him. 'Torquemada is here himself.' Torquemada was now the Grand Inquisitor for all of Spain. 'Even with Brother Torquemada's famed efficiency, the courts have yet to process more than a handful of cases. But we are making progress.'

James's soul turned at this brusque summary. Since he had last visited Spain he had found out more about Ferron, who, as it turned out, was from a converso family himself – and Grace, of course, likely had her veins polluted by Saracen blood. Was this why they were so enthusiastic about the Inquisition's dreadful cleansing? For no matter how hard they scrubbed, they could not remove the impurities from their own bodies.

Ferron went on, 'In the meantime, lady, we have business to discuss. I told you the Inquisition has ears and eyes everywhere. We are almost as ubiquitous as God Himself, our admirers say – and our enemies. I believe we may have found your Dove. Come, we must talk.' He offered his arm, and they walked off, without looking back to see if James and Abdul followed.

Friar Ferron escorted them to the palace of the Moorish governor of Ronda, called the Mondragon, which had been given over to officers of the Inquisition. The palace was only a short walk along the road that followed the cliff top. They walked through light-filled rooms to a colonnaded courtyard, and then passed on through a horseshoe arch into a small garden that overlooked the cliff itself, with a remarkable view of the flood plain below.

The mudejar Abdul brought out a tray of tea.

Grace glanced at Abdul. 'Are you sure it's safe to talk of these matters in front of him?'

'The mudejar? Of course. He is an ambassador to one defeated Moorish city from another which soon will be defeated. What harm can he do? We will speak freely, and forget he even exists.'

Grace leaned forward eagerly. 'Tell me of this Dove, then.'

Ferron said, 'I cast a net for men of his sort, and have caught what looks like a promising fish. He came to our attention – I mean the Inquisition's – because he intends to travel to Cordoba, to the monarchs' court, where he hopes to present his case.'

'A case to do what?'

Ferron smiled. 'To sail the Ocean Sea. To go west, if he can.'

'Then such a man exists,' Grace breathed.

'Oh, yes. He was born in Genoa, this man, the son of a clothier. He is now thirty-four years old. It seems he was educated in a school run by the clothiers' guild. But his learning is poor,' he said dismissively. 'He was restless, as many of that Italian breed are. He ran off to sea; he served on ships from his youth. He has sailed to Chios in the Aegean, and as far as Iceland in the Ocean Sea; he has visited Ireland, England, Flanders, and sailed down the African coast. He became a competent navigator, mapmaker and ship's master, it seems. He made his money from his petty bits of commerce, as men of his kind do.

'But his fortunes changed, this poor Dove's, when he made a good marriage. He wed into a noble Portuguese family called Perestrelo. And this is where the dream was born. For his father-in-law, who died before the Dove married his daughter, served as a captain during the colonisation of Madeira, led by Henry the Navigator. The Perestrelos were given some land on the island of Porto Santo, off Madeira. Here it was that our Dove settled with his wife, and he began to go through his dead father-in-law's maps and accounts of his explorations. He learned first hand how a new land may be made to turn a profit for its discoverer, and the nation that sponsors him.

'And his eyes were drawn west. Porto Santo, I am told, is a haven for those who sail out into the fringe of the Ocean Sea in their little ships, explorers hunting down the African coast, slavers seeking a supply base. And many of them bring back tales of marvellous lands which lie to the west, always just out of sight…'

Out of all these fragments, in the head of the clothier's son, a most remarkable dream was born.

Ferron said, 'Perhaps if you sail west and keep on sailing, it would be more than new lands, new Madeiras, that you would find. For if the world is round, then perhaps you could sail around it. Perhaps you would end up coming around the curve of the earth and arrive in the east…'

James was astounded. He was educated; he knew his geography, and the shape of the world. But this was a category of journey that had never occurred to him before. 'Can it be possible?'

'Oh, yes,' Ferron said. 'Why, it was a dream of Pedro, elder brother of Henry the Navigator, half a century ago. And there are strong commercial reasons to try it. Some say that if the Muslims block the way to the east – well, then, on a round world, perhaps a route can be found to the far east, by sailing west.'

'And that is the Dove's dream,' Grace said.

Ferron sneered. 'You can just see this little man, the jumped-up Genoan, his poorly educated mind struggling to make sense of the tavern legends he so credulously devours. But he is devout, I'll give him that. It's not just trade he's after. He's said to have concocted a scheme to contact the Mongol Khan, if he still reigns, and to persuade him to join an attack on the Islamic states from the east. Our clothier's son dreams of liberating Jerusalem!'