Outside, in St. Mildred's Lane, we came upon Cobbett, who stood looking on as his old dog pissed copiously against the wall of the college.

"Afternoon, Doctor Bruno!" he called cheerfully, raising a hand in salute. "Off to bandy words with the rector?"

"Buona sera, Cobbett." I gestured casually to the gatehouse behind us. "I see they are clearing the tower room."

Cobbett chuckled. "They don't hang about with these matters, the senior rooms are great prizes here. Doctor Coverdale wants to move in as soon as possible."

"He is to take over as subrector, then?"

"It's not official yet, but that won't stop him. Come on, now, Bessie, home again." The old dog had finished her business and was hobbling painfully toward the gate, Cobbett ushering her gently along. "Oh, by the bye, Doctor Bruno-here is another mystery for you." He grinned, showing decayed gums.

"What is that?" I turned back, eager for information.

"That spare key to Doctor Mercer's room I said had been taken from my lodge-well, Master Slythurst brought it to me this morning. Found it on the northwest staircase just outside the tower room, he says. Whoever took it must have let it fall there the day before and not noticed-it is gloomy on those stairs at the best of times. Well, at least I have the full complement back again ready for our new subrector."

"On the staircase? But how did the bursar come to find it there?" I asked, wondering how Slythurst had covered this lie.

"I suppose he was on his way to the strong room." He shuffled to the gate and pushed it open, then turned back to me. "Good luck with your disputation, sir," he added. "And may the best man win."

"Thank you," I said, but I was distracted by this new information. It now seemed almost certain that Slythurst had taken that missing key and used it to let himself into Mercer's room: if he had truly been there on official business he would have had no need to confect such a story for the porter.

"Sir, we…ah…do need to hasten our steps, you are expected at five," Weston said awkwardly. I nodded and ran my hands through my hair as if to untangle my thoughts; it would not do to have my brains running on locks and keys while I was supposed to be disputing the laws of the cosmos in front of all Oxford.

"Yes, I am sorry. Let us make haste-you lead the way," I said.

"They were saying you were right there this morning, sir, when Gabe Norris shot the dog. Did you see the whole thing?"

Weston spoke with a boyish excitement, looking at me eagerly as he showed the way into Brasenose Lane, a narrow alley running along the north side of the college. Here the ground was muddy underfoot and the alley smelled as if it were a favourite place to piss. I took a deep breath and followed him.

"I was there, yes. But we were all too late-something for which I cannot forgive myself. Young Norris is a true shot. If we had been just a few moments earlier, poor Doctor Mercer might have stood a chance."

Weston pursed his lips. "Aye, well-the likes of Gabe Norris have nothing else to do with their time except practise their sports. It won't matter a jot to him whether he even takes his degree- Oxford is just one more amusement to his sort, strutting about in his London finery. Not so for us poor scholars obliged to go into the Church, alas." He laughed bitterly.

"You don't like him, I deduce?" I said, smiling.

Weston appeared to relent.

"Oh, he's all right. I resent the commoners in principle-in a community of scholars one should feel oneself among equals, and their presence reinforces the notion of degree. And it is galling the way most of them don't care for their studies at all. But Gabe Norris is not the worst-he is quite generous with his fortune really, and not as stupid as some. Do you know, he has his own horse, sir?" Weston paused, shaking his head with a young man's envy. "A roan gelding, the finest creature you ever saw. He stables it outside the city walls, for students are not supposed to keep their own mounts. But he does what he likes, for who would punish him?"

"He does seem very sure of himself," I agreed. "I imagine he gets more than his fair share of women, too, with that face."

Weston only turned his head to glance at me, a sly grin curling at the corners of his mouth.

"You might imagine so, aye," he said, and his peculiar emphasis, together with the mischievous smile, caught my attention.

"Ah," I said, guessing at his meaning. "You mean to say that women are not Master Norris's principal area of interest?"

"I would speak no slander against him, sir. I have no idea what he does in private, it is only what is said."

"Much may be said in envy," I observed as we walked. "Why is it said of him, do you know?"

Weston looked down, embarrassed. "Well, for one, he does not like to visit the bawdy houses, sir."

"It does not follow that he is therefore a sodomite." Privately, though, it would not surprise me to learn that it was true of Norris, with his dandyish ways. I remembered the curious look he had given me when I mentioned Saint Bernardino's tirade against sodomites. "And you should be careful with such gossip-sodomy is a hanging offence in this country, is it not?"

"Yes, sir. You are right, of course." Weston looked chastened. "But we have all noticed it. If a beautiful girl makes eyes at you like a calf, while you show yourself so entirely indifferent, it cannot be that you have a man's blood, would you not say, sir?" His cheeks were flushed crimson, and I guessed from this outburst that he was speaking of matters close to home. Since there was only one female in the immediate orbit of the young scholars, it was not hard to figure whom he meant.

"You are talking of the rector's daughter?" It should not have surprised me; as the only young woman in the college, why should she not set her fancy at the handsomest of the rich young men there? Yet I felt somehow disappointed by the revelation, as if I had imagined a girl with Sophia's quick mind would not be blinded by such superficial qualities. "She has confided in you?"

"Oh no, sir-and I have said too much already."

He tried to change the subject but at that moment I stopped abruptly, realising that we were now at the end of Brasenose Lane and the wall running to our right was the wall of Lincoln Grove. The thick wooden door set into the wall was firmly shut. This must have been where the dog was released into the garden.

"Wait a moment," I said, crouching down to examine the mud around the base of the door. It was undoubtedly churned up, but the passage of feet in the wet ground since the morning had obliterated any clear trace of prints and I cursed myself for not having had the wit to go and look for evidence straightaway. I stood up and tried the handle to the door; it was locked. I was about to turn away when something caught my eye among the tufts of grass growing at the foot of the gate. I crouched again and drew out a thin leather strap, torn at one end-the kind of strap one might use for muzzling a dog. I did not know what use it might be, but I slipped it into my pocket just in case.

"Sir, we shall be late." Weston seemed agitated, but I had noticed him watching me with curiosity as I pocketed the strap. "Just at the end of the lane, and we are almost there."

We passed into a wide square bordered by St. Mary's church to the right and, just visible to the left, above the wall of Exeter College garden, the pinnacles of the Divinity School. Ahead I could see the bulk of the city wall, its crenellated battlements outlined against the sky. Rounding the corner, we were dwarfed by the spectacular facade of the Divinity School and I paused to admire it, craning my neck up to the turrets above the grand arched window. Usually only ecclesiastical buildings were designed in such splendour, but here was a secular edifice built like a cathedral, consecrated to the pursuit of knowledge, quite equal to the grand church of San Domenico Maggiore in Naples where I had first learned the art of disputation. To think that my ideas would join the echoes in its magnificent vaults was almost humbling, and I was about to make a remark to that effect to my guide, when I prickled with the discomfiting sense that I was being watched. I turned and saw, leaning up against the blackened stone of the city wall, a tall man with folded arms, staring at me quite blatantly. He was dressed in an old leather jerkin and breeches of worn brown cloth, his hair was severely receded on top but long at the back, leaving his large forehead bare, and his face was pitted with the marks of pox. He might have been my own age or he might have been fifty, but the most striking aspect of his appearance was that he had no ears. Ugly welts of scar tissue surrounded the holes where they would once have been, betraying the fact that he had at one time been brought to justice as a petty criminal. He continued to watch me with a cool, level gaze in which I could discern no malice, rather a kind of mocking curiosity. I wondered if he was staring at me in particular, or if he were an opportunist pickpocket or some such, on the lookout for opportunity among the crowds gathering for the disputation. I had noted on my travels through Europe how petty thieves always seem to assume that men of education are necessarily also men of wealth; in my experience the two are rarely found together. If so, the man was bold; a further arrest for theft and he would risk the rope.