s on his mind as much as if he had left her only yesterday. His memories of her were painfully vivid, although he had not seen her for more than a year. He could recall any of her expressions at will: laughing, thoughtful, suspicious, anxious, pleased, astonished, and--clearest of all--passionate. He had forgotten nothing about her body, and he could still see the curve of her breast, feel the soft skin on the inside of her thigh, taste her kiss, and smell the scent of her arousal. He often longed for her.

To cure himself of his fruitless desire he sometimes imagined what Aliena must be doing. In his mind's eye he would see her pulling Alfred's boots off at the end of the day, sitting down to eat with him, kissing him, making love to him, and giving her breast to a baby boy who looked just like Alfred. These visions tortured him but did not stop him from longing for her.

Today, Christmas Day, Aliena would roast a swan and re-dress it with its feathers for the table, and there would be posset to drink, made of ale, eggs, milk, and nutmeg. The food in front of Jack could not have been more different. There were mouth-watering dishes of strangely spiced lamb, rice mixed with nuts, and salads dressed with lemon juice and olive oil. It had taken Jack awhile to get used to Spanish cooking. They never served the great joints of beef, legs of pork and haunches of venison without which no feast was complete in England; nor did they consume thick slabs of bread. They did not have the lush pastures for grazing vast herds of cattle or the rich soil on which to grow fields of waving wheat. They made up for the relatively small quantities of meat by imaginative ways of cooking it with all kinds of spices, and in place of the ubiquitous bread of the English they had a wide variety of vegetables and fruits.

Jack was living with a small group of English clerics in Toledo. They were part of an international community of scholars that included Jews, Muslims and Arab Christians. The Englishmen were occupied translating works of mathematics from Arabic into Latin, so they could be read by Christians. There was an atmosphere of feverish excitement among them as they discovered and explored the treasure-house of Arab learning, and they had casually welcomed Jack as a student: they admitted into their circle anyone who understood what they were doing and shared their enthusiasm for it. They were like peasants who have labored for years to scratch a crop out of poor soil and then suddenly move to a rich alluvial valley. Jack had abandoned building to study mathematics. He had not yet needed to work for money: the clerics casually gave him a bed and any meals he wanted, and they would have provided him with a new robe and sandals if he had needed them.

Raschid was one of their sponsors. As an international trader he was multilingual and cosmopolitan in his attitudes. At home he spoke Castilian, the language of Christian Spain, rather than Mozarabic. His family also all spoke French, the language of the Normans, who were important traders. Although he was a man of commerce, he had a powerful intellect and a wide-ranging curiosity. He loved to talk to scholars about their theories. He had taken a liking to Jack immediately, and Jack dined at his house several times a week.

Now, as they began to eat, Raschid asked Jack: "What have the philosophers taught us this week?"

"I've been reading Euclid." Euclid's Elements of Geometry had been one of the first books translated.

"Euclid is a funny name for an Arab," said Ismail, Raschid's brother.

"He was Greek," Jack explained. "He lived before the birth of Christ. His work was lost by the Romans but preserved by the Egyptians--so it comes to us in Arabic."

"And now Englishmen are translating it into Latin!" Raschid said. "This amuses me."

"But what have you learned?" said Josef, the fiance of Raya.

Jack hesitated. It was hard to explain. He tried to make it practical. "My stepfather, the builder, taught me how to perform certain operations in geometry: how to divide a line exactly in half, how to draw a right angle, and how to draw one square inside another so that the smaller is half the area of the larger."

"What is the purpose of such skills?" Josef interrupted. There was a note of scorn in his voice. He saw Jack as something of an upstart, and was jealous of the attention Raschid paid to Jack's conversation.

"Those operations are essential in planning buildings," Jack replied pleasantly, pretending not to notice Josef's tone. "Take a look at this courtyard. The area of the covered arcades around the edges is exactly the same as the open area in the middle. Most small courtyards are built like that, including the cloisters of monasteries. It's because these proportions are most pleasing. If the middle is bigger, it looks like a marketplace, and if it's smaller, it just looks as if there's a hole in the roof. But to get it exactly right, the builder has to be able to draw the open part in the middle so that it's precisely half the area of the whole thing."

"I never knew that!" Raschid said triumphantly. He liked nothing better than to learn something new.

"Euclid explains why these techniques work," Jack went on. "For example, the two parts of the divided line are equal because they form corresponding sides of congruent triangles."

"Congruent?" Raschid queried.

"It means exactly alike."

"Ah--now I see."

However, no one else did, Jack could tell.

Josef said: "But you could perform all these geometric operations before you read Euclid--so I don't see that you're any better off now."

Raschid protested: "A man is always better off for understanding something!"

Jack said: "Besides, now that I understand the principles of geometry I may be able to devise solutions to new problems that baffled my stepfather." He felt rather frustrated by the conversation: Euclid had come to him like the blinding flash of a revelation, but he was failing to communicate the thrilling importance of these new discoveries. He changed tack somewhat. "It's Euclid's method that is the most interesting," he said. "He takes five axioms--self--evident truths--and deduces everything else logically from them."

"Give me an example of an axiom," Raschid said.

"A line can be prolonged indefinitely."

"No it can't," said Aysha, who was handing round a bowl of figs.

The guests were somewhat startled to hear a girl joining in the argument, but Raschid laughed indulgently: Aysha was his favorite. "And why not?" he said.

"It has to come to an end sometime," she said.

Jack said: "But in your imagination, it could go on indefinitely. "

"In my imagination, water could flow uphill and dogs speak Latin," she retorted.

Her mother came into the room and heard that rejoinder. "Aysha!" she said in a steely voice. "Out!"

All the men laughed. Aysha made a face and went out. Josef's father said: "Whoever marries her will have his hands full!" They laughed again. Jack laughed too; then he noticed they were all looking at him, as if the joke was on him.

After dinner, Raschid showed off his collection of mechanical toys. He had a tank in which you could mix water and wine and they would come out separately; a marvelous water-driven clock, which kept track of the hours in the day with phenomenal accuracy; a jug that would refill itself but never overflow; and a small wooden statue of a woman with eyes made of some kind of crystal that absorbed water in the warmth of the day and then shed it in the cool of the evening, so that she appeared to be weeping. Jack shared Raschid's fascination with these toys, but he was most intrigued by the weeping statue, for whereas the mechanisms of the others were simple once they had been explained, no one really understood how the statue worked.

They sat in the arcades around the courtyard in the afternoon, playing games, dozing, or talking idly. Jack wished he belonged to a big family like this one, with sisters and uncles and in-laws, and a family home they could all visit, and a position of respect in a small town. Suddenly he recalled the conversation he had had with his mother the night she rescued him from the priory punishment cell. He had asked her about his father's relations, and she had said Yes, he had a big family, back in France. I have got a family like this one, somewhere, Jack realized. My father's brothers and sisters are my uncles and aunts. I might have cousins of my own age. I wonder if I will ever find them?

He felt adrift. He could survive anywhere but he belonged nowhere. He had been a carver, a builder, a monk and a mathematician, and he did not know which was the real Jack, if any. He sometimes wondered if he should be a jongleur like his father, or an outlaw like his mother. He was nineteen years old, homeless and rootless, with no family and no purpose in life.

He played chess with Josef and won; then Raschid came up and said: "Give me your chair, Josef--I want to hear more about Euclid."

Josef obediently gave up his chair to his prospective father-in-law, then moved away--he had already heard everything he ever wanted to know about Euclid. Raschid sat down and said to Jack: "You're enjoying yourself?"

"Your hospitality is matchless," Jack said smoothly. He had learned courtly manners in Toledo.

"Thank you; but I meant with Euclid."

"Yes. I don't think I succeeded in explaining the importance of this book. You see--"

"I think I understand," Raschid said. "Like you, I love knowledge for its own sake."

"Yes."

"Even so, every man has to make a living."

Jack did not see the relevance of that remark, so he waited for Raschid to say more. However, Raschid sat back with his eyes half closed, apparently content to enjoy a companionable silence. Jack began to wonder whether Raschid was reproaching him for not working at a trade. Eventually Jack said: "I expect I shall go back to building, one day."

"Good."

Jack smiled. "When I left Kingsbridge, riding my mother's horse, with my stepfather's tools in a satchel slung across my shoulder, I thought there was only one way to build a church: thick walls with round arches and small windows topped by a wooden ceiling or a barrel-shaped stone vault. The cathedrals I saw on my way from Kingsbridge to Southampton taught me no different. But Normandy changed my life."

"I can imagine," Raschid said sleepily. He was not very interested, so Jack recalled those days in silence. Within hours of landing at Honfleur he was looking at the abbey church of Jumieges. It was the highest church he had ever seen, but otherwise it had the usual round arches and wooden ceiling--except in the chapter house, where Abbot Urso had built a revolutionary stone ceiling. Instead of a smooth, continuous barrel, or a creased groin vault, this ceiling had ribs which sprang up from the tops of the columns and met at the apex of the roof. The ribs were thick and strong, and the triangular sections of ceiling between the ribs were thin and light. The monk who was keeper of the fabric explained to Jack that it was easier to build that way: the ribs were put up first, and the sections between were then simpler to make. This type of vault was also lighter. The monk was hoping to hear news from Jack of technical innovations in England, and Jack had to disappoint him. However, Jack's evident appreciation of rib-vaulting pleased the monk, and he told Jack that there was a church at Lessay, not far away, that had rib-vaulting throughout.

Jack went to Lessay the next day, and spent all afternoon in the church, staring in wonder at the vault. What was so striking about it, he finally decided, was the way the ribs, coming down from the apex of the vault to the capitals on top of the columns, seemed to dramatize the way the weight of the roof was being carried by the strongest members. The ribs made the logic of the building visible.

Jack traveled south, to the county of Anjou, and got a job doing repair work at the abbey church in Tours. He had no trouble persuading the master builder to give him a trial. The tools he had in his possession showed that he was a mason, and after a day at work the master knew he was a good one. His boast to Aliena, that he could get work anywhere in the world, was not entirely vain.

Among the tools he had inherited was Tom's foot rule. Only master builders owned these, and when the others discovered Jack had one, they asked him how he had become a master at such a young age. His first inclination was to explain that he was not really a master builder; but then he decided to say he was. After all, he had effectively run the Kingsbridge site while he was a monk, and he could draw plans just as well as Tom. But the master he was working for was annoyed to discover that he had hired a possible rival. One day Jack suggested a modification to the monk in charge of the building, and drew what he meant on the tracing floor. That was the beginning of his troubles. The master builder became convinced that Jack was after his job. He began to find fault with Jack's work, and put him on the monotonous task of cutting plain blocks.

Soon Jack set off again. He went to the abbey of Cluny, the headquarters of a monastic empire that spread all across Christendom. It was the Cluniac order that had initiated and fostered the now-famous pilgrimage to the tomb of Saint James at Compostela. All along the Compostela road there were churches dedicated to Saint James and Cluniac monasteries to take care of pilgrims. As Jack's father had been a jongleur on the pilgrim road, it seemed likely he had visited Cluny.

However, he had not. There were no jongleurs at Cluny. Jack learned nothing about his father there.

Nevertheless, the journey was by no means wasted. Every arch Jack had ever seen, until the moment he entered the abbey church of Cluny, had been semicircular; and every vault had been either tunnel-shaped, like a long line of round arches all stuck together, or groined, like the crossing where two tunnels met. The arches at Cluny were not semicircular.

They rose to a point.

There were pointed arches in the main arcades; the groined vaults of the side aisles had pointed arches; and--most startling of all--above the nave there was a stone ceiling that could only be described as a pointed barrel vault. Jack had always been taught that a circle was strong because it was perfect, and a round arch was strong because it was part of a circle. He would have thought that pointed arches were weak. In fact, the monks told him, the pointed arches were considerably stronger than the old round ones. The church at Cluny seemed to prove it, for despite the great weight of stonework in its peaked vault, it was very high.

Jack did not stay long at Cluny. He continued south, following the pilgrim road, diverging whenever the whim took him. In the early summer there were jongleurs all along the route, in the larger towns or near the Cluniac monasteries. They recited their verse narratives to crowds of pilgrims in front of churches and shrines, sometimes accompanying themselves on the viol, just the way Aliena had told him. Jack approached every one and asked if he had known Jack Shareburg. They all said no.

The churches he saw on his way through southwest France and northern Spain continued to astonish him. They were all much higher than the English cathedrals. Some of them had banded barrel vaults. The bands, reaching from pier to pier across the vault of the church, made it possible to build in stages, bay by bay, instead of all at once. They also changed the look of a church. By emphasizing the divisions between bays, they revealed that the building was a series of identical units, like a sliced loaf; and this imposed order and logic on the huge interior space.

He was in Compostela at midsummer. He had not known there were places in the world that were so hot. Santiago was another breathtakingly tall church, and the nave, still under construction, also had a banded barrel vault. From there he went farther south.

The kingdoms of Spain had been under Saracen rule until recently; indeed, most of the country south of Toledo was still Muslim-dominated. The appearance of Saracen buildings fascinated Jack: their high, cool interiors, their arcades of arches, their stonework blinding white in the sun. But most interesting of all was the discovery that both rib-vaulting and pointed arches featured in Muslim architecture. Perhaps this was where the French had got their new ideas.

He could never work on another church like Kingsbridge Cathedral, he thought as he sat in the warm Spanish afternoon, listening vaguely to the laughter of the women somewhere deep in the big cool house. He still wanted to build the most beautiful cathedral in the world, but it would not be a massive, solid, fortress-like structure. He wanted to use the new techniques, the rib-vaults and the pointed arches. However, he thought he would not use them in quite the way they had been used so far. None of the churches he had seen had made the most of the possibilities. A picture of a church was forming in his mind. The details were hazy but the overall feeling was very strong: it was a spacious, airy building, with sunlight pouring through its huge windows, and an arched vault so high it seemed to reach heaven.

"Josef and Raya will need a house," Raschid said suddenly. "If you were to build it, other work would follow."

Jack was startled. One thing he had not thought of building was houses. "Do you think they want me to build their house?" he said.

"They might."

There was another long silence, during which Jack contemplated life as a housebuilder for wealthy merchants in Toledo.

Eventually Raschid seemed to come awake. He sat upright and opened his eyes wide. "I like you, Jack," he said. "You're an honest man, and you're worth talking to, which is more than can be said for most people I've met. I hope we will always be friends."

"So do I," said Jack, somewhat surprised by this un-prompted tribute.

"I'm a Christian, so I don't keep my women locked away, as some of my Muslim brothers do. On the other hand, I'm Arab; which means I don't give them quite the ... forgive me, the license, that other women are used to. I allow them to meet and talk with male guests at the house. I even allow friendships to develop. But at the point where friendship begins to ripen into something more--as happens so naturally among young people--then I expect the man to make a formal move. Anything else would be an insult."

"Of course," Jack said.

"I knew you'd understand." Raschid stood up and put an affectionate hand on Jack's shoulder. "I've never been blessed with a son; but if I had, I think he would have been like you."

On impulse, Jack said: "But darker, I hope."

Raschid looked blank for a moment, then he roared with laughter, startling the other guests around the courtyard. "Yes!" he said merrily. "Darker!" And he went into the house, still guffawing.

The older guests began to take their leave. Jack sat by himself, thinking over what had been said to him, as the after