New books? I was surprised by the discovery. What on earth could the mistress of Pontifex Hall want with yet more books? I was sitting in one of the chairs now, riffling the leaves of the first volume with a mixture of curiosity and guilty pleasure. What choice texts, I wondered, might she have brought with her? Learned tomes like Ficino's translations of Plato or Hermes Trismegistus? Or volumes on witchcraft, or perhaps even necromancy?

But each of them covered more mundane territories, ones hardly preferable, in my opinion, to the company of the dour and surly Phineas Greenleaf. I frowned at the title-pages as I plucked up the volumes and then replaced them. All were on matters pertaining to the business of wills and property law. The names were familiar enough, but never had I troubled myself to open one of them, let alone to read as much as a page. Yet here, with a bookmark fully three-quarters of the way through, was Hobhouse's A Treatise of Testaments and Last Wills, while beneath it sat Blackacre's notoriously dull A Touchstone of Property and Conveyances. Its pages had been cut all the way to the bitter end, as had those in the third volume, Phillimore's gargantuan Equity Law and the Practice of the Court of Chancery. Only the last book seemed in keeping with the Lady Marchamont I thought I knew: a volume entitled The Law's Resolution of Women's Rights. Its pages too had been cut from front to back, while the notes scratched in the margin were composed in a familiar hectic scrawl.

By now a light tread was squeaking across the ceiling overhead. I replaced the last volume and sat back in the chair, aching with exhaustion. I had still not recovered either from my exertions-I had spent most of the morning and a good part of the afternoon in Alsatia-or from the shock of my discovery. I scrubbed my palms across my cheeks and brow, then took a couple of deep gulps as if drinking the dense, mulled air of the room from a heavy gourd. I fished the copy of Agrippa's Magische Werke carefully from my pocket and placed it on the table next to the other books. Yes, I had come far today. I had learned much.

Closing my eyes, I heard the soft outcry of treads and risers as Alethea descended the staircase. I sat back to await her arrival. How much, I wondered, ought I to tell her?

I had left for Alsatia early that morning, this time travelling upriver by sculler. Arrowsmith Court, when I finally found it, proved exactly the kind of place in which I would have expected Pickvance to conduct his unsavoury trade: a small patch of mud-slimed cobbles round three sides of which a number of sooty tenements pressed four and five storeys upwards. A clowder of scrawny cats was busy in a heap of fishbones, while a couple of others groomed themselves in doorways and on window-sills. Last night's rain had collected in turbid pools and already stank like bilgewater. As I picked my way round them a chamber-pot was emptied from one of the upper windows. I leapt sideways in the nick of time. Yes, I thought ruefully: I had come to the right place.

The Saracen's Head stood directly opposite the courtyard's narrow, arched entrance. A swarthy, moustachioed face, its expression fierce and implacable, peered back at me from a signboard above the door. The tavern itself appeared to be closed. A tobacconist's stood to one side of it, a shop of more ambiguous designation on the other, both were also shut tight, their bottle-glass windows bleared with dirt and soot. Beside the tobacconist's door stood another, smaller door, whose tarnished amuel-and-brass sign read: 'Dr. Pickvance-Bookseller Auctioneer'.

After pulling a fraying bell-rope I was admitted with much furtiveness and then conducted up five flights of stairs by Mr. Skipper, who explained that Dr. Pickvance was otherwise engaged, but that he, Mr. Skipper, would be honoured to assist. The 'offices', from what I was allowed to see of them, consisted of a single room furnished with two desks, a pair of chairs, and what looked to be the tools of a bookbinder's trade: a stack of sheepskins and a beating-stone in a far corner, together with an assortment of gimlets, sewing-presses and polishing irons littered across the rest of the room. There was also a printing-press, an enormous mechanical beast to which Mr. Skipper repaired after sitting me at one of the desks. On the desk sat a pile of perhaps two dozen catalogues bound in greasy brown leather.

'Good luck to you,' he murmured with a morose smile, then turned his back, I suppose to begin cobbling together more 'masterpieces' for Pickvance's next auction. I picked up the first of the volumes and opened its cover.

As I read through the catalogues for the next eight hours, nourished only by an unappetising rabbit pie fetched by Mr. Skipper from a cookshop, a few facts about the mysterious Dr. Pickvance gradually began taking shape. I was able to determine that he conducted his auctions roughly twice a year, going back as far as 1651, the year when the Civil War ended and the Blasphemy Act passed through Parliament. All of the auctions must have been as clandestine as the one in the Golden Horn, because all had been conducted in Alsatia, roughly half in the Golden Horn, the others scattered among a handful of nearby taverns and alehouses, including two or three in the Saracen's Head. The works auctioned had been of a piece, it seemed, with those sold in the Golden Horn, and some of the auctions had comprised as many as 500 lots. The catalogues listed each work's author, title, date of impression, style of binding, number of pages and illustrations, general condition, and, finally, provenance. I was encouraged by this last detail. I noticed how Pickvance or some amanuensis had recorded not only the name of whoever put the lot up for auction but also that of whoever had purchased it.

I suspected, however, that many of these names and provenances were as fraudulent as the books themselves, for 1651 was the year that Cromwell sequestrated many Royalist estates, and I guessed that the contents of their libraries-or else volumes featuring their forged ex-librises-had passed through Pickvance's office. I noticed that one of the catalogues for an auction in 1654 advertised 'books once belonging to Sir George VILLIERS, Duke of BUCKINGHAM, removed from his admirable collection at York House in the Strand'. I knew that part of this 'admirable collection'-truly, one of the choicest in Europe-had been looted after the Civil War when York House was confiscated; the other half had been sold at auction a few years later when Buckingham's son, the second Duke, a Royalist, ran short of funds during his exile in Holland. But whether or not Pickvance had been selling bona fide volumes stolen from Buckingham's collection it was impossible, on the evidence of the catalogues, to discern.

My heart lurched as I looked at the dozens of titles in the York House collection. Ours was an age of great discrimination and taste, of aesthetes and collectors such as Buckingham and the late King Charles, but it was also an age of great desecration. How many treasures like those of Buckingham must have been lost to England because of our wars? Because of the Puritans and their superstitious zealotry? For when Cromwell and his cohorts weren't destroying works of art-beheading statues or tossing paintings by Rubens into the Thames-they were selling them two-a-penny to the agents of the King of Spain and Cardinal Mazarin, perhaps even to unscrupulous merchants like Dr. Pickvance. I noticed that a number of lots in Pickvance's catalogues had come from the salerooms of Antwerp, which for the past few decades had been the clearing-house from which plunder from the numerous European wars was sold at starvation prices to the greedy princes of Europe. As I reached for another volume I quailed at the task now confronting me. How on earth was I to find The Labyrinth of the World in such a mountain of other stolen volumes?