'Anything for us?'

'One letter, sir.'

'Well? Let us have it, then.'

'He made me pay tuppence for it.'

'Pardon me?'

'The clerk.' He extended his hand. 'He said it was undertaxed, sir. Not a paid letter, he said. So I had to pay tuppence.'

'Very well.' I set Don Quixote aside, remunerated Monk with a show of irritation, then seized the letter. 'Now off with you. Go fetch the coal.'

I was expecting to hear from Monsieur Grimaud, my factor in Paris, who had been instructed to bid on my behalf for a copy of Vignon's edition of the Odyssey. But I saw immediately that the letter, a single sheet tied with string and embossed with a seal, bore the green stamp of the Inland Office rather than the red one of the Foreign Office. This was peculiar, because domestic mail arrived at the General Letter Office on Mondays, Wednesdays and Fridays. For the moment, however, I thought little of this oddity. The Post Office was in a state of upheaval like everything else. Already many of the old postmasters-Cromwell's busiest spies, so the rumours went-had been relieved of their positions, and the Postmaster-General, John Thurloe, was clapped up in the Tower.

I turned the letter over in my hand. In the top, right-hand corner a stamped mark read '1^st July', which meant that the letter had arrived in the General Letter Office two days earlier. My name and address were inscribed across it in a secretary hand, slantwise and hectic. The writing was blotched in some places and faint in others, as if the ink was old and powdery or the goose quill splayed at the nib or worn to a stump. The oblong impression of a signet ring on the reverse bore a coat of arms with the legend 'Marchamont'. I cut the frayed string with my penknife, broke the seal with my thumb and unfolded the sheet.

I still possess this strange letter, my summons, the first of the many texts that led me towards the ever-receding figure of Sir Ambrose Plessington, and I reproduce it here, word for word:

28^th June

Pontifex Hall

Crampton Magna

Dorsetshire

My good Sir:

I trust you will forgive the impertinence of a Lady writing to a stranger to make what will seem, I have no doubt, a peculiar request; but circumstances force the expediency upon me. These melancholy affairs are of a pressing nature, but I believe you can play no small part in their resolution. I dare not enumerate further details until I have your more private attentions, and must therefore, with regret, depend entirely on your trust.

My request is for your presence at Pontifex Hall at the earliest possible convenience. To this end a coach driven by Mr. Phineas Greenleaf will be waiting for you beneath the sign of the Three Pigeons in High Holborn, at 8 o'clock in the morning of the 5^th of July. You have nothing to apprehend from this journey, which I promise shall be made worth your while.

Here I must break off, with the assurance that I am, dear Sir, with gratitude,

Your most obliging servant,

Alethea Greatorex

Postscriptum: Let this caution regulate your actions: neither mention to anyone your receipt of this letter, nor disclose to them your destination or purpose.

That was all, nothing more. The strange communication offered no further information, no further inducements. After reading it through once more, my first response was to crumple it into a ball. I had no doubt that the 'melancholy' and 'pressing' business of Alethea Greatorex involved disposing of a crumbling estate entailed upon her by a late indigent husband. The sorry appearance of the unpaid letter suggested the impecunious condition of its author. No doubt Pontifex Hall comprised among its meagre charms a library with whose modest contents she hoped to appease her creditors. Requests of this variety were not unusual, of course. The sad business of assigning values to the dire remains of bankrupt estates-mostly those of old Royalist families whose fortunes had tumbled low during Cromwell's time-had three or four times fallen within the compass of my duties. Usually I purchased the better editions myself, then sent the rest of the worm-eaten lot to auction, or else to Mr. Hopcroft, the rag-and-bone man. But never in the course of my duties had I been engaged under such secretive terms or required to travel as far as Dorsetshire.

And yet I didn't discard the letter. One of the more cryptic phrases-'I dare not enumerate further details'-had snagged my imagination, as did the plea in the postscript for secrecy. I pushed my spectacles further up the bridge of my nose and once again fixed the letter with a myopic squint. I wondered why I should feel I had something to 'apprehend' from the journey and how the vague promise that it would be worth my time might fulfil itself. The profit to which the words alluded seemed at once grander and vaguer than any vulgar financial transaction. Or was this simply my imagination, anxious as usual to weave and then unpick a mystery?

Monk had disposed of the rubbish in the ash-can and was now returning through the door with a few lumps of sea coal clattering in his pail. He set it on the floor, sighed, picked up his broom and brushed apathetically at a beam of sunlight. I laid the letter aside, but a second later took it up to study more closely the secretary hand, an old-fashioned style even for those days. I read the letter again, slowly, and this time its text seemed less explicable, less certainly the appeal of a financially embarrassed widow. I spread it on the counter and studied the crested seal more closely, regretting the haste with which I broke it, for the legend was no longer decipherable.

And it was at this point that I noticed something peculiar about the letter, one more of its strange and, for the moment, inexplicable traits. As I held the paper to the light I realised that the author had folded the paper twice and sealed it not with wax but a rust-coloured shellac. This was not unusual in itself, of course: most people, myself included, sealed their letters by melting a stick of shellac. But as I gathered the flakes and tried to reconstruct the image impressed by the matrix I noticed how the shellac was mingled with a substance of a slightly different colour and composition: something darker and less adherent.

I moved the letter into the beam of light falling across my counter. Monk's broom rasped slowly across the floorboards, and I became aware of his curious gaze. I prised at the seal with the blade of my penknife as gently as an apothecary slicing the seed pod of a rare plant. The compound crumbled and then sprinkled over the counter. A beeswax was clearly distinguishable from the shellac into which, for whatever reason, it was mingled. I carefully separated a few of the grains, puzzled that my hand seemed to be trembling.

'Is there something wrong, Mr. Inchbold?'

'No, Monk. Nothing at all. Back to work with you now.'

I straightened and gazed over his head, out of the window. The narrow street was busy with its morning commerce of bobbing heads and revolving wheels. Dust was raised from the carriageway and, caught in the slats of morning sunlight, turned to gold. I lowered my eyes to the flakes on the counter. What, if anything, might the mixture mean? That Lady Marchamont's matrix bore a residue of wax? That she had closed another letter with a beeswax only moments before sealing mine with shellac? It hardly made sense. But then neither did the alternative: that someone had moulded her original wax seal, broken it, then closed it with shellac impressed by a counterfeit seal.

My pulses quickened. Yes, it seemed most likely that the seal had been tampered with. But by whom? Someone in the General Letter Office? That might explain the delay in its delivery-why it was available on a Tuesday instead of a Monday. There were rumours that letter-openers and copyists worked out of the top floor of the General Letter Office. But to what purpose? So far as I knew, my correspondence had never been opened before-not even the packets sent by my factors in Paris and Oxford, those two bastions of Royalist exiles and malcontents.