One day I would write all this in a book that would be my life's work, a book that would send such ripples through Christendom, as Copernicus's De revolutionibus orbium coelestium had done, but greater still, a book that would undo all the certainties not only of the Roman church but of the whole Christian religion. But there was still so much more that I needed to understand, too many books I had yet to read, books of astrology and ancient magic, all of which were forbidden by the Dominican order and which I could never obtain from the library at San Domenico Maggiore. I knew that if I were to stand before the Holy Roman Inquisition now, all of this would be pricked out of me with white-hot irons, with the rack or the wheel, until I vomited my hypothesis out half cooked, whereupon they would burn me for heresy. I was twenty-eight years old; I did not want to die just yet. I had no choice but to run.

It was just after compline; the monks of San Domenico were preparing to retire for the night. Bursting into the cell I shared with Fra Paolo of Rimini, trailing the cold of the night on my hair and habit, I rushed frantically about the tiny room, gathering what few belongings I had into an oilskin bag. Paolo had been lying in contemplation on his straw pallet when I flung the door open; now he propped himself up on one elbow, watching my frenzy with concern. He and I had joined the monastery together as novices at the age of fifteen; now, thirteen years later, he was the only one I thought of as a brother in the true sense.

"They have sent for the Father Inquisitor," I explained, catching my breath. "There is no time to lose."

"You missed compline again. I told you, Bruno," Paolo said, shaking his head. "If you spend so many hours in the privy every night, people will grow suspicious. Fra Tomasso has been telling everyone you have some grievous disease of the bowel-I said it would not take long for Montalcino to deduce your true business and alert the abbot."

"It was only Erasmus, for Christ's sake," I said, irritated. "I must leave tonight, Paolo, before I am questioned. Have you seen my winter cloak?"

Paolo's face was suddenly grave.

"Bruno, you know a Dominican may not abandon his order, on pain of excommunication. If you run away, they will take it as a confession, they will put out a warrant for you. You will be condemned as a heretic."

"And if I stay I will be condemned as a heretic," I said. "It will hurt less in absentia."

"But where will you go? How will you live?" My friend looked pained; I stopped my searching and laid my hand on his shoulder.

"I will travel at night, I will sing and dance or beg for bread if I have to, and when I have put enough distance between myself and Naples, I will teach for a living. I took my doctor of theology last year-there are plenty of universities in Italy." I tried to sound cheerful, but in truth my heart was pounding and my bowels were turning to water; it was somewhat ironic that I could not now go near the privy.

"You will never be safe in Italy if the Inquisition name you as a heretic," Paolo said sadly. "They will not rest until they see you burned."

"Then I must get out before they have the chance. Perhaps I will go to France."

I turned away to look for my cloak. There flashed into my memory, as clear as the day it was first imprinted, the image of a man consumed by fire, his head twisted back in agony as he tried in vain to turn his face from the heat of the flames that tore hungrily at his clothes. It was that human, fruitless gesture that stayed with me in the years afterward-that movement to protect his face from the fire, though his head was bound to a stake-and since then I had deliberately avoided the spectacle of another burning. I had been twelve years old, and my father, a professional soldier and a man of orthodox and sincere belief, had taken me to Rome to watch a public execution for my edification and instruction. We had secured a good vantage point for ourselves in the Campo dei Fiori toward the back of the jostling crowd, and I had been amazed at how many had gathered to make profit from the event as if it were a bearbaiting or a fair: sellers of pamphlets, mendicant friars, men and women peddling bread and cakes or fried fish from trays around their necks. Neither had I expected the cruelty of the crowd, who mocked the prisoner with insults, spitting and throwing stones at him as he was led silently to the stake, his head bowed. I wondered if his silence were defeat or dignity, but my father explained that he had an iron spike driven through his tongue so that he could not try to convert the spectators by repeating his foul heresies from the pyre.

He was tied to the stake and the faggots piled around him so that he was almost hidden from view. When a torch was held to the wood, there was an almighty crackling and the kindling caught light immediately and burned with a fierce glow. My father had nodded in approval; sometimes, he explained, if the authorities feel merciful, they allow green wood to be used for the pyre, so that the prisoner will often suffocate from the smoke before he truly suffers the sting of the flames. But for the worst kind of heretics- witches, sorcerers, blasphemers, Lutherans, the Benandanti-they would be sure the wood was as dry as the slopes of Monte Cicala in summer, so that the heat of the flames would tear at the offender until he screamed out to God with his last breath in true repentance.

I wanted to look away as the flames rushed to devour the man's face, but my father was planted solidly beside me, his gaze unflinching, as if watching the poor wretch's agonies were an essential part of his own duty to God, and I did not want to appear less manly or less devout than he. I heard the mangled shrieks that escaped the condemned man's torn mouth as his eyeballs popped, I heard the hiss and crackle as his skin shrivelled and peeled away and the bloody pulp beneath melted into the flames, I smelled the charred flesh that reminded me horribly of the boar that was always roasted over a pit at street festivals in Nola. Indeed, the cheering and exultation of the crowd when the heretic finally expired was like nothing so much as a saint's day or public holiday. On the way home I asked my father why the man had had to die so horribly. Had he killed someone, I wondered? My father told me that he had been a heretic. When I pressed him to explain what a heretic was, he said the man had defied the authority of the pope by denying the existence of Purgatory. So I learned that, in Italy, words and ideas are considered as dangerous as swords and arrows, and that a philosopher or a scientist needs as much courage as a soldier to speak his mind.

Somewhere in the dormitory building I heard a door slam violently.

"They are coming," I whispered frantically to Paolo. "Where the devil is my cloak?"

"Here." He handed me his own, pausing a moment to tuck it around my shoulders. "And take this." He pressed into my hand a small bone-handled dagger in a leather sheath. I looked at him in surprise. "It was a gift from my father," he whispered. "You will have more need of it than I, where you are going. And now, sbrigati. Hurry."

The narrow window of our cell was just large enough for me to squeeze myself onto the ledge, one leg at a time. We were on the first floor of the building, but about six feet below the window the sloping roof of the lay brothers' reredorter jutted out enough for me to land on it if I judged the fall carefully; from there I could edge my way down a buttress and, assuming I could make it across the garden without being seen, climb the outside wall of the monastery and disappear into the streets of Naples under cover of darkness.

I tucked the dagger inside my habit, slung my oilskin pack over one shoulder, and climbed to the ledge, pausing astride the windowsill to look out. A gibbous moon hung, pale and swollen, over the city, smoky trails of cloud drifting across its face. Outside there was only silence. For a moment I felt suspended between two lives. I had been a monk for thirteen years; when I lifted my left leg through the window and dropped to the roof below, I would be turning my back on that life for good. Paolo was right; I would be excommunicated for leaving my order, whatever other charges were levelled at me. He looked up at me, his face full of wordless grief, and reached for my hand. I leaned down to kiss his knuckles when I heard again the emphatic stride of many feet thundering down the passageway outside.