Where to begin amid such chaos? The room was crammed with furniture of assorted sizes and shapes, all made from good oak. Chairs had been turned over, a trunk dragged across the floor and forced open to reveal a cache of books. The apparent desperation of the searcher proved beyond any doubt that he believed there was something of significance to be found among Mercer's possessions; the question was whether it had already been found, and if not, whether I would know it if I saw it.

I turned to the handsome writing desk, now littered with papers and quills. A little brass astrolabe had been knocked to the floor in the frenzy. I bent to retrieve it and set it back on its stand, but its rule was broken. As I crouched I noticed a dark curling object under the desk; its shape was unusual, but when I reached to pick it up and brought it into the light, I saw that it was only a length of orange peel, long dried out, and threw it back to the floor. Lifting one or two of the top sheets, I skimmed the papers on the desk; it would be painstaking work to sift through the mass of leaves piled up there for any letter or jotting that might shed light on the former occupant's death. All the drawers of the desk had been pulled out; I reached into each one, feeling along the underside for any catches that would release secret compartments, but found nothing. I lifted out contents of the drawers abandoned in disarray, but already I felt daunted by the task; I had no idea what I hoped to find.

From the top left-hand drawer I withdrew a fine leather writing case and briefly tensed with hope, thinking that perhaps Mercer's most recent correspondence might still be within and might reveal whom he had lately fallen out with or any transactions that could explain his presence in the garden. I cleared a space on the desk for the case and as I opened it, a thin, cloth-bound book fell out. Picking it up, I opened it at random and saw that it was a printed almanac for the year 1583, the pages marked into divisions for the days of the week, the month marked at the top of each page and annotated with the relevant astrological predictions. My pulse racing in my throat, I flicked hastily through to the page for today's date, wondering if there was the slightest chance he might have noted whom he had planned to meet this morning.

As I searched for the page marked May 22, I noticed an oddity about this calendar: each division was marked with two dates, one printed in black, the second marked in by hand in red ink. The red date was ten days ahead of the black. I knew immediately what this meant because my host, the French ambassador, worked from such calendars in the embassy: the red number showed the date according to the new calendar introduced the previous year in February by Pope Gregory, now mandatory in the Catholic states by order of the papal bull Inter gravissimas. It had not been adopted by England and the other Protestant countries of Europe as a marked act of defiance to papal authority, but I had often heard the ambassador complaining that it made correspondence between the officials of different countries extremely confusing, because no one was quite sure which date was meant; usually he would use both, just to be sure. But why, I wondered, would an English Protestant like Roger Mercer need a calendar marked with the Gregorian dates?

I found the page I wanted and was moved to see that on May 22 (June 1) he had written the time and place of my disputation in his elegant, sloping hand: "G Bruno vs. Underhill, Div. Sch. 5." Then, holding the book closer, I noticed another mark for today's date; in the top left-hand corner of the day's division there was a solitary letter "J." I blinked in disbelief. Could J be the initial of the person he had arranged to meet? That could certainly narrow it down. I scoured recent dates for any other clues. The previous day, the twenty-first (thirty-first) was marked only with a curious symbol, a circle with spokes like the wheel of a cart. Flicking back through the book, I noticed this symbol appeared on other pages at regular intervals; more or less once every ten days, though never on the same day of the week. It might have been a code, but I had no way of deciphering it. The J, though, did at least seem a concrete clue.

But as I had held the book up to my nose, I had noticed something else: a faint smell of oranges. I thought at first that it came from my own fingers, having picked up the peel from the floor, but as I sniffed I realised that the smell was coming from the almanac itself. Perhaps that was not unusual; if Roger Mercer liked to eat oranges, it was likely that he had spread the juice to the pages of his books; he had not been the most fastidious eater, as I had noted the night before. But something nagged at my mind, and as I sniffed the book again I suddenly cursed myself for being so stupid.

At that moment, the wardrobe door creaked a little farther on its worn hinge, making me jump almost out of my boots. Instinctively I hid the book inside my shirt, tucked into the waist of my breeches, and whipped around, but the door appeared to have moved under its own weight. Opening it right up, I saw at first only heaps of cloth, half pulled out by the hasty searcher, and then I made out a squat dark shape pushed up against the back of the closet, covered by an old blanket. When this was yanked away, it revealed a small wooden chest bound with iron bands and fastened with a sturdy padlock. Reaching in, I dragged the object into the light, but it tilted and landed with a resounding thud as it dropped between the ledge of the wardrobe and the floor. I paused, my breath held tight in my throat, to see if the noise had alerted anyone to my presence in the room, but all was silent. As the chest fell, I had heard unmistakably the metallic clink of coins. So this was Roger Mercer's strongbox, his treasury, plainly full of gold. He had not taken much trouble to conceal it, and yet it had been left untouched by whoever had laid waste to his room.

This fitted with the full purse left on Mercer's body; it seemed clear that whoever had killed him was not interested in taking money. But why else does a man kill, if not for money? Either for revenge, I thought, or because he fears the victim may do him harm. I decided I would have to visit the porter, Cobbett, and see what he could tell me of the college's system of gates and locks; the person who had turned this room upside down had evidently let himself in with a key and locked the room again behind him.

As I crouched beside the trunk brooding on the matter of keys, I heard the undeniable click of the lock in the room behind me turning smoothly and my heart almost froze in my chest. There was no time to hide; all I could do was watch helplessly as the door slid open just wide enough to admit the lanky figure of Walter Slythurst, the bursar. I watched as his gaze slowly swept the tumult of the room with incredulity before eventually coming to rest on me. There was even a brief pause as his brain struggled to process the evidence of his ferrety eyes, before he gave a little cry and stared at me as if I were an apparition.

"Almighty God!" he exclaimed. "You! What the Devil-?"

It was going to take a quite exceptional feat of invention to explain why I had locked myself into the recently ransacked room of a newly dead man and was now cradling his strongbox in my blood-soaked lap. I took a deep breath and affected nonchalance.

"Buongiorno, Master Slythurst."

Slythurst's face, all planes and angles, was made for sneering cynicism rather than purple rage, but at this moment he appeared to swell up to a point where he could barely formulate his own language.

"What-?" he began, before his gathered breath escaped in a squeaking hiss, and he inhaled for the next attempt. "What is this?"

"I am assisting the rector," I explained, exaggerating my accent, which I had found in the past to be a useful cover for apparently eccentric behaviour; people put it down to the oddities of a foreigner. "I was with him this morning, we were the first to arrive at the scene of the terrible misfortune. And the clothes, you see, were badly destroyed, so I have come to find some replacements in which to dress the poor body of Doctor Mercer for his final rest." I assumed a pious expression; never had I uttered so unconvincing a lie. In his place, I would not have believed me for a moment.