It was a very strange letter. Very strange indeed. It had been brought to John Rawlings, Apothecary, by Fred, the general factotum of the shop in Shug Lane, Piccadilly, who hung round nosily while John broke the wax that sealed it. He looked up.

'When did this arrive?'

'Just now, Sir. The post boy brought it. I took it from his hand directly.'

'I see.'

Fred still stood, staring beadily.

'Haven't you got any work to do?'

'No, Sir. I've swept the floor and the shop is all clean and tidy.'

'Well sweep through again. There is no such thing as too clean.'

Fred reluctantly went off to fetch his broom and John looked at the letter.

Honourable Sir. I beg you though you do not know the Signatory to peruse these words. I can claim only the slightest Connection with your Goodself and that is through a cousin of Your Friend Samuel Swann Esq. I believe that you have helped to solve Problems with the Esteemed Magistrate Sir John Fielding and I now wonder if you can help me Solve One of a personal Nature with which I am confronted.

My Wife sadly Passed From this Life some Six Years ago. She had Been Married before and I met her Son, who lived with us until he ran away from home aged Fourteen Years. Despite our best Endeavours, he refused to return Home. My Wife, under the terms of Her Will, had left her Son – her only Child – a considerable fortune in Diamond jewellery and of this he was advised by My Lawyer, Who put an Advertisement in Several Newspapers. Accordingly, He arrived in this Country some Months Ago to take Receipt of His Inheritance.

I come to the Point. I did not recognise Him at all. It was as if a Stranger had Walked into My House. He had Changed out of all Recognition. When he knocked upon My door I first refused Him Entry but he called out Jovially, "Do you not Know Me?" and I was forced to let him in. Sir, I Beg of You a Favour. Please could You Come to the small village of Clifton, outside Bristol, and help me Somehow to Identify this Man.

I shall, my dear and Honoured Sir, Be Most Grateful if this could be done at some time in the Not Too distant Future.

John read the signature – 'Horatio Huxtable, Merchant' – then put the letter into the pocket of his long apron.

'Anyfing interesting?' asked Fred, peering over his broom.

'You haven't swept the corners,' answered John with a grin, and walked into his compounding room.

He was greeted immediately by the sweet smell of drying herbs, bunches of which hung from a beam running the length of the chamber. Looking round him, he felt in seventh heaven. Everything that constituted his art was around him: alembics, crucibles, retorts and matrasses stood on a bench near the back, while on the centre table were small oil stoves with bubbling pewter pans upon them, and several pestles and mortars, in the largest of which Robin Hazell was pounding away at a mixture of simples. John sighed. He might be a lonely widower, but in this place he could put his troubles behind him and feel at peace with the world.

Robin was now eighteen years old and had grown into the most attractive young man. Delicately built and not terribly tall, his autumnal colouring and sherry eyes had lost the naivety of youth and now appeared to make him look like an elegant faun. His hands were graceful and in them something as ordinary as a pestle contrived to become a thing of beauty. John felt protective of him, realising that the boy could well be the prey of depraved creatures of either sex.

Robin looked up as the Apothecary came into the room.

'All well, Master?'

'Yes indeed. How is that mixture coming along?'

'It's almost done.'

'Good. Let it stand overnight and we will boil it for the decoction in the morning.'

'Very well, Sir.'

John looked around him and despite the harmony he had with his surroundings, felt the first shiver of cold. It was a September evening and the nights were getting sharp. He looked at his fob watch which told him that there was another quarter of an hour until closing. Going back into the shop and seeing that it was empty – Fred having disappeared upstairs to tidy the rooms of the law students who lived above – the Apothecary opened the letter once more. The address was given as '24, Sion Row, the village of Clifton, near Bristol', the date a week previously.

The Apothecary pondered. He could ask Gideon Purle, his former apprentice, now an apothecary in his own right and a Yeoman of the Worshipful Society of Apothecaries, if he could run the shop while he went away, and he knew that Gideon would agree. But the snag about this was that young Purle devoted all his time to running John's sparkling water business in company with Jacquetta Fortune, the wretchedly thin widow whom John had asked to manage the project, and who had surprisingly blossomed into an elfin beauty with frosty lights in her golden hair.

Whether the two were in love the Apothecary had never been able to work out. Their heads were always bent close together as they leaned over sales figures and the like. Yet though he was sure his former apprentice had strong yearnings in that direction, Mrs Fortune always remained intriguingly unreadable.

How like a woman, John thought, and smiled cynically.

Once more he looked at his watch, somewhat battered nowadays after its many years of service. It had been given to him by Sir Gabriel Kent, his beloved adopted father, on his twenty-first birthday – all those years ago, the Apothecary thought, and laughed a little at the very idea.

It was nearly time to close the shop and Fred came in for his final instructions.

'Anything more to do, Sir?'

'All swept and clean for the morning?'

'Yessir.'

'Then you can pull the cover over the counter and leave the rest to Robin and me.'

'Very good, Mr Rawlings,' and Fred's hand came up into a salute.

As usual the gesture tugged at the Apothecary's heartstrings. As a baby, Fred had been dumped in a box outside the gates of Thomas Coram's Foundling Hospital and had been taken on by John out of the goodness of his heart. One day, or so he hoped, Fred would make a fine servant to someone of position, but meanwhile the little lad was acting as a general cleaner and dogsbody for the Apothecary's shop and the law students in the dwelling above. He watched as the boy pulled at the linen cover and called Robin out to help.

'Is it time to go, Master?'

'Yes. It's a cold night and I doubt we'll get any more custom.'

While the boys struggled with the cloth, John went into the compounding room and blew out the candles and oil lamps, then went into the shop and did the same. Then, having seen Fred scuttle up the stairs, he locked the door and stepped out into the night.

There was little joy left in his home, he thought as he walked along, Robin hurrying beside him. Number 2, Nassau Street, that had once been so full of love and laughter, was a quiet house now, only the ghosts of the past left to whisper down the corridors at night.

Sir Gabriel Kent, once the greatest beau in London, had long since moved to the village of Kensington, while Rose, John's beloved daughter, was at boarding school in Kensington Gore. Gideon, too, had rented a small apartment over a shop in Thrift Street now that he was no longer an apprentice. Young Robin, as custom decreed, slept in the servants' quarters in John's house. So the only other person in the...