'Take us out of here immediately,' I commanded the driver.

'Yes, sir.'

The hack shunted forward, negotiated a dog's-leg, rounded a bend, then crept through a tight street bordered on either side by decrepit buildings whose window-panes were filmed with grease and soot. The road was cratered with pot-holes, a few of which had been imperfectly repaired with brushwood. No one seemed to be about. The Thames lay to our right, parallaxing into view every now and then across vacant, rubble-littered lots, its front lined by a number of precarious-looking wharves. Black ghosts of coal dust hurried across our path. We kept a course parallel to the river, the hack swaying from side to side as the wooden-toothed Jehu on the box-seat picked our way recklessly round an obstacle course of desquamated roof-tiles, shattered bits of quern-stone and the iron hoops and broken staves of long-emptied kegs of ale. Soon I could smell the mud of the Fleet; then a minute later its bank cut us off, and we turned on to a path that did not, to my eyes, look like leading back up to Fleet Street.

'For God's sake, man!'

'Another minute, sir…'

But after another minute we were still bumping and swaying on the path, downwind of the constipated river, our wheels squelching in the mud. The Fleet's surface was scummed over and clouds of insects hung in the air. I covered my nose with a handkerchief and held my breath.

All at once, however, I caught sight through the window of something that looked familiar, a bit of graffito-the work of a child?-scrawled in chalk across a dead wall, thus:

I craned my neck as we lumbered slowly past. What did this peculiar hieroglyph mean? Was it the caricature of a man? A horned man? Perhaps the devil? I was certain I had seen the figure somewhere before. But where? In a book?

'Damn!'

I swung round and peered up at the box-seat. 'What is it?'

'Apologies, sir.' The hack had stopped moving. 'We seem to have reached a dead end.'

'A dead end-?'

The graffito was forgotten. I flung open the door, stepped outside and immediately sank halfway to my ankles in some sort of ooze. The horses, too, stood fetlock-deep in sludge and the wheels of the hack were buried to their rims. I raised my eyes. I could see ahead of us the bell-tower of Bridewell Prison and the steeple of St. Bride's, but little else other than a cluster of sheds in the gathering shadows. It was later than I had realised, for the sun was dipping behind the irregular serrulations of Whitehall Palace, and here and there among the buildings a few rush-lights had begun to flicker. Alsatia was coming awake.

'Allow me, sir.'

The driver tossed his whip aside and hopped down from his box, giving me an ingratiating smile. He had almost guided me back inside, when I looked up from the mire to see that a light had appeared in the window of the building nearest us: a tavern, from the look of it. Its signboard creaked faintly in the breeze. I squinted at its inscription. I could make out the head of some sort of animal and a wink of gold paint.

'Come along, sir.' The driver's hands pressed my shoulders. 'Sir? Is everything all right?'

'Yes…' I barely heard him. I was pressing a shilling into his palm, not looking at him. 'Here-your money. Take it.' I was already walking towards the tavern. 'Now go.'

I heard his incredulous voice behind me: 'Sir?'

'Go!'

The mud sucked at my boots and I had to wrench them free at each step. But a few seconds later I was on solid ground, a bricked footpath, and the tavern rose before me. The door opened, throwing a triangle of light across the bricks. I was moving forward, squinting at the signboard. And, once again I saw the peeling portrait, clearer now: the head of a buck whose antlers had been painted gold. Above the antlers, three words: THE GOLDEN HORN.

Chapter Four

It was the smell that struck me first, stale pipe and coal smoke mingled with sawdust and vermiculated wood daubed with pitch: the smell of a chamber that had seen neither broom nor beeswax, neither light nor air. Then, as I stepped inside and my pupils adapted to the dim light, I caught what became the most pervasive scent of all: coffee. For the Golden Horn wasn't a tavern after all, but a coffee-house.

The door swung shut behind me and I took a few more steps through the hearth smoke, casting about for a chair. A coffee-house was the last thing I expected to find in the heart of Alsatia, though I shouldn't really have been surprised, because even then, as far back as 1660, it seemed that a coffee-house stood in every street. I had only ever been inside one of them, the Greek's Head, an airy place filled with would-be actors and poets, and its congenial atmosphere could not possibly have prepared me for the smoke and gloom of the Golden Horn.

I found a seat, a three-legged stool, and sat down well away from the fire, which was drawing poorly.

'Your pleasure, sir?'

A short and pot-bellied waiter had appeared beside me, wiping his hands on a grubby apron. Behind him, two unsavoury-looking men sat in grave discussion, while behind them a lone man, the one who had entered a moment earlier, sat with his back to us, paring the calluses on his palms with a knife. As I looked around me at the crude furniture, the tiny hearth, the curled handbills yellowing on the walls, I wondered what tangled thread could possibly connect the Golden Horn to Pontifex Hall. All at once I doubted whether the patterns I was seeing-the cipher, the keyword, the strange verse, Strabo, now the Golden Horn coffee-house-had any significance beyond my own imagination. Was there a meaning behind this series of clues, or only chance and coincidence?

There was only one way to find out. I reached into my pocket and withdrew a penny. 'A dish of coffee, please.'

But no clues or mysterious powers revealed themselves; at least, not yet. By the time I finished the drink-a bitter, sludgy brew-the room had filled with more customers. A dozen-odd men had arrived, singly or in twos, each of them shabbily dressed, with scuffed boots and patched coats. Conversation was sporadic and quiet, punctuated by guttural laughter. The waiter moved back and forth from the counter to the tables, dishes clattering on his tray. Everyone seemed to be waiting for something to happen, but nothing did. I had been wrong about the significance of the name; it must have been a coincidence, nothing more. There were probably half a dozen taverns or coffee-houses called The Golden Horn, none of which had any connection with Pontifex Hall, least of all this one.

It was only after a few more minutes that I noticed the cabinet. It stood in the corner of the room, a small cabinet of rarities of the sort used by proprietors to attract custom. But from my seat I could see how this particular case was a sorrier collection than most, a witch's cupboard unlikely to convince even the most gullible patron. But I was curious, if not gullible, so I rose from my chair and crossed the floor.

The corner was darker than elsewhere, and no one else was paying the least bit of attention to the half-hearted display. Misspelled cards inscribed in a shaky hand identified a half-dozen uninspiring objects that seemed to cringe behind the glass. I leaned forward, squinting through my spectacles. A worm-eaten piece of cloth was identified as part of Edward the Confessor's shroud, while, beside it, an unremarkable wooden branch, half rotted, was reported as coming from a tree against which glanced the arrow that killed King William Rufus. According to its label, another even more undistinguished fragment had been chipped from the tomb of Sebert, King of the Saxons.

I almost burst out laughing at the sight of these bogus fragments of history, but then another of the cards caught my eye. Yellowed and curling, propped at the back of the cabinet, it identified a few square inches of frayed canvas as part of the main topsail of the Britomart, one of the ships in Sir Walter Raleigh's Orinoco expedition of 1617. I frowned and leaned forward again. I doubted the scrap was any more authentic than the others, but it reminded me of the patent in the coffin at Pontifex Hall, the one for the construction of the Philip Sidney.