Sir Francis Walsingham. Queen Elizabeth's principal secretary of state, the man behind my unlikely presence on this royal visitation to Oxford; even his name made my spine prickle.

We walked a little farther from the body of the crowd gathered to marvel as the barge was decked with flowers for our departure. Beside it, a group of musicians had struck up a dance tune, and we watched the crowd milling around them.

"But now tell me, Bruno-you have not set your sights upon Oxford merely to debate Copernicus with a host of dull-witted academicians," Sidney continued, in a low voice. "I knew as soon as I heard you had come to England that you must be on the scent of something important."

I glanced quickly around to be sure no one was within earshot.

"I have come to find a book," I said. "One I have sought for some time, and now I believe it was brought to England."

"I knew it!" Sidney grabbed my arm and drew me closer. "And what is in this book? Some dark art to unlock the power of the universe? You were dabbling in such things in Padua, as I recall."

I could not tell whether he was mocking me still, but I decided to trust to what our friendship had been in Italy.

"What would you say, Philip, if I told you the universe was infinite?"

He looked doubtful. "I would say that this goes beyond even the Copernican heresy, and that you should keep your voice down."

"Well, this is what I believe," I said, quietly. "Copernicus told only half the truth. Aristotle's picture of the cosmos, with the fixed stars and the six planets that orbit the earth-this is pure falsehood. Copernicus replaced the earth with the sun as the centre of the cosmos, but I go further: I say there are many suns, many centres-as many as there are stars in the sky. The universe is infinite, and if this is so, why should it not be populated with other earths, other worlds, and other beings like ourselves? I have decided it will be my life's work to prove this."

"How can it be proved?"

"I will see them," I said, looking out over the river, not daring to watch his reaction. "I will penetrate the far reaches of the universe, beyond the spheres."

"And how exactly will you do this? Will you learn to fly?" His voice was sceptical now; I could not blame him.

"By the secret knowledge contained in the lost book of the Egyptian sage Hermes Trismegistus, who first understood these mysteries. If I can trace it, I will learn the secrets necessary to rise up through the spheres by the light of divine understanding and enter the Divine Mind."

"Enter the mind of God, Bruno?"

"No, listen. Since I saw you last I have studied in depth the ancient magic of the Hermetic writings and the Cabala of the Hebrews, and I have begun to understand such things as you would not believe possible." I hesitated. "If I can learn how to make the ascent Hermes describes, I will glimpse what lies beyond the known cosmos-the universe without end and the universal soul, of which we are all a part."

I thought he might laugh then, but instead he looked thoughtful.

"Sounds like dangerous sorcery to me, Bruno. And what would you prove? That there is no God?"

"That we are all God," I said, quietly. "The divinity is in all of us and in the substance of the universe. With the right knowledge, we can draw down all the powers of the cosmos. When we understand this, we can become equal to God."

Sidney stared at me in disbelief.

"Christ's blood, Bruno! You cannot go about proclaiming yourself equal to God. We may not have the Inquisition here, but no Christian church will hear that with equanimity-you will be straight for the fire."

"Because the Christian church is corrupt, every faction of it-this is what I want to convey. It is only a poor shadow, a dilution of an ancient truth that existed long before Christ walked the earth. If that were understood, then true reform of religion might be possible. Men might rise above the divisions for which so much blood has been spilled, and is still being spilled, and understand their essential unity."

Sidney 's face turned grave. "I have heard my old tutor Doctor Dee speak in this way. But you must be careful, my friend-he collected many of these manuscripts of ancient magic during the destruction of the monastic libraries, and he is called a necromancer and worse for it, not just by the common people. And he is a native Englishman, and the queen's own astrologer too. Do not get yourself a reputation as a black magician-you are already suspicious as a Catholic and a foreigner." He stepped back and looked at me with curiosity. "This book, then-you believe it is to be found in Oxford?"

"When I was living in Paris, I learned that it was brought out of Florence at the end of the last century and, if my adviser spoke the truth, it was taken by an English collector to one of the great libraries here, where it lies unremarked because no one who has handled it has understood its significance. Many of the Englishmen who travelled in Italy were university men and left their books as bequests, so Oxford is as good a place as any to start looking."

"You should start by asking John Dee," Sidney said. "He has the greatest library in the country."

I shook my head. "If your Doctor Dee had this book, he would know what he held in his hands, and he would have made this revelation known by some means. It is still to be discovered, I am certain."

"Well, then. But don't neglect Walsingham's business in Oxford." He slapped me on the back again. "And for Christ's sake don't neglect me, Bruno, to go ferreting in libraries-I shall expect some gaiety from you while we are there. It's bad enough that I must play nursemaid to that flatulent Pole Laski-I'm not planning to spend every evening with a clutch of fusty old theologians, thank you. You and I shall go roistering through the town, leaving the women of Oxford bowlegged in our wake!"

"I thought you were to marry Walsingham's daughter?" I raised an eyebrow, feigning shock.

Sidney rolled his eyes. "When the queen deigns to give her consent. In the meantime, I do not consider myself bound by marriage vows. Anyway, what of you, Bruno? Have you been making up for your years in the cloister on your way through Europe?" He elbowed me meaningfully in the ribs.

I smiled, rubbing my side.

"Three years ago, in Toulouse, there was a woman. Morgana, the daughter of a Huguenot nobleman. I gave private tuition to her brother in metaphysics, but when her father was not at home she would beg me to stay on and read with her. She was hungry for knowledge-a rare quality in women born to wealth, I have found."

"And beautiful?" Sidney asked, his eyes glittering.

"Exquisite." I bit my lip, remembering Morgana's blue eyes, the way she would try and coax me to laughter when she thought I grew too melancholy. "I courted her in secret, but I think I always knew it was only for a season. Her father wanted her to marry a Huguenot aristocrat, not a fugitive Italian Catholic. Even when I became a professor of philosophy at the University of Toulouse and finally had the means of supporting myself, he would not consent, and he threatened to use all his influence in the city to destroy my name."

"So what happened?" Sidney asked, intrigued.

"She begged me to run away with her." I sighed. "I almost allowed myself to be persuaded, but I knew in my heart that it would not have been the future either of us wanted. So I left one night for Paris, where I ploughed all my energies into my writing and my advancement at court. But I often wonder about the life I turned my back on, and where I might have been now…" My voice trailed away as I lowered my eyes again, remembering.

"Then we should not have had you here, my friend. Besides, she's probably married to some aging duke by now," Sidney said heartily.

"She would have been," I agreed, "had she not died. Her father arranged a marriage to one of his friends but she had an accident shortly before the wedding. Drowned. Her brother wrote and told me."