Mr Kleist did his best to kick M. Pamplemousse accidentally on purpose as he turned away, but the creature easily avoided his foot and mewed with what sounded like self-satisfaction.

I sniff, blow my nose, look round. I am in another version of the building which housed the Perineum Club, back where Lord Harmyle is – at this very moment, I should think – lying on the floor, kicking and gurgling his way to a rather bloody death.

In this reality, the Vermyn Street building contains a parfumerie. The dark wood panels are mostly hidden by exquisite wall rugs and creamy, gently glowing light panels illuminating a smattering of tear-shaped perfume bottles arrayed on glass shelves. The air is laced with enchanting female scents and no one looks in the least surprised that I have just sneezed. The well-heeled clientele is composed mostly of ladies. One or two are with gentlemen, and there are a couple of other unescorted men besides myself. It is the men I find myself looking at. The shop assistants are mostly very good-looking young men. One especially chiselled specimen, tall and dark, smiles at me. I smile back, a little thrill running through me.

Ah well. I never fully appreciate being gay, but at least I haven’t hit the ground counting the cracks in the parquet flooring. I seem to have left the OCD behind, for now at least. My languages are English, Spanish, Portuguese, French, German and Cantonese, plus smatterings.

I quickly review my attire in a full-length mirror. I am dressed similarly to the way I was with Lord Harmyle (I wonder if he is the late Lord Harmyle yet). My hair is long and dark and ringleted in what would appear to be the fashion here, though it looks particularly good on me, I must say. No wonder the young assistant favoured me with a smile. I check my hands for any signs of blood. It would be unusual and alarming if there were any, but one always looks. Spotless. I have very pale hands, beautifully manicured and sporting two silver or white gold rings on each hand.

I have no time to dally. One further regretful smile at the handsome young assistant and I make for the door, checking my wallet, papers and ormolu pill box as I go. I am Mr Marquand Ys, according to my British passport. That is all in order. The wallet is full of large white banknotes and several important-looking bits of plastic with silvery chips embedded.

Into the street. Still no airships. Dommage!

However: above the relatively low-rise buildings a very large aircraft sails serenely overhead, heading west. I wave my cane at a cab – a whirring, hunchbacked-looking thing which I’d surmise runs off electricity – and order the lady cabbie to take me to the airport.

In the mirror, the woman’s brow creases. “Which one?”

Ah, a large London; Londres grande! How splendid. “Where’s that aircraft heading?” I ask, pointing with my cane.

She cranes her neck out of her window, squinting. “Eafrow, I should fink.”

“There, then.”

“It’ll cost ya.”

“I’m sure. Now do drive on.” We set off. “Plyte, Jésusdottir, Krijk, Heurtzloft-Beiderkern, Obliq, Mulverhill,” I mutter. It feels pleasing to me, just saying it. It has a become a mantra, I suppose. The girl cabby glances askance at me in her mirror. “Plyte, Jésusdottir, Krijk, Heurtzloft-Beiderkern, Obliq, Mulverhill,” I repeat, smiling.

“Wottevah, mate.”

I sit back, watching the relatively quiet traffic and rather loud architecture glide past. My heart has been beating rather rapidly since my transition – well, since Lord Harmyle’s murder, I suppose. Now it begins to slow, allowing me the luxury of reflection.

Of course I think about whatever poor wretch I’ve left behind to deal with the aftermath of my actions, especially when it is something as dramatic and unpleasant as a murder. What must it be like for them, I wonder? Allegedly they know nothing about what has happened until after I have gone, though I always wonder if this is really true. Might they not be aware of what I am making them do, even as I do it? Are they not perhaps along for the ride when I take over their body, observing – doubtless terrified and frustrated – as I perform whatever actions I deem to be necessary to fulfil whatever orders I have been given?

Or are they genuinely oblivious, and effectively wake up to be suddenly confronted with – in the case of the operation just concluded – a dying man, blood on their hands and the stares of shocked witnesses? What could one possibly do in such circumstances? Flinch back, horrified, exclaiming, “But it wasn’t me!”? Scarcely supportable. One would do best to run, I’d imagine. It might be better for the poor bastards to collapse, quite dead, the instant I leave them. I have asked about this kind of thing, but the Concern is by its nature very conservative and secretive and even the researchers, technicians and experts whose business it is to know of such matters are not inclined to divulge the relevant answers.

There are those who assuredly do know the answers to all these questions and more. Madame d’O would know; Mrs M would too, and Dr Plyte and Professore Loscelles and all the others on the Central Council. There is in all likelihood an entire division of the… hmm, for some reason I don’t want to think of it as the Concern. This is one of the worlds where it is thought of as l’Expédience.

Anyway, indeed. There is an entire cadre of experts who have studied what happens when someone like myself takes over a previously existing person in another reality and then leaves them again, but l’Expédience does not deem me to be one of those who needs to know the results of their research. I’d love to know. I have carried out my own modest experiments, attempting to rummage round in the memories I find or the feelings I discover, trying to find some trace of the personality I have displaced, but so far such vicarious introspections have produced nothing except a lingering feeling of foolishness at having undertaken them in the first place.

Plainly I inherit something of the character of the person whose being I usurp. That must be where the OCD comes from, and one’s sexual inclination, as does the taste for, variously, coffee, tea, chocolate, spiced milk, hard liquor, bland or spicy food, or prunes. I have found myself, over the years, surveying the reality I find myself in with the eyes of somebody who is plainly a general medical practitioner, a surgeon, a landscape designer, a mathematician, a structural engineer, a livestock breeder, a litigation lawyer, an insurance assessor, an hotelier and a psychiatrist. I seem to be at home amongst the professions. Once I was a sewerage system designer who was also a serial killer. (Yes, I know, but I would beg the indulgence of being regarded, rather, as an assassin. I will even accept Paid Killer, so long as it is understood that I do what I do through informed choice rather than due to some grubbily psychotic urge. Though I’ll allow that the importance of this distinction might escape my victims.) On that occasion I had to suppress the urge to strangle prostitutes in order to carry out my mission, which was to track down and kidnap (ha! You see? Not kill) my quarry.

On the other hand, I have never been a woman, which is slightly odd and even a little disappointing. Obviously there are limits.

And are these bodies I inhabit ever used more than once? I have never visited the same body twice – indeed, I rarely visit the same reality twice.

These taken-over persons will have had perfectly full lives before I invade them. They have pasts, careers, networks of relationships both personal and professional; all that one would expect. I have had “my” wives, partners, girlfriends, “my” children and “my” best friends greet me without a trace of discomfiture or any sign that I am behaving oddly or out of character. I seem to know how to behave when I am somebody else, as naturally as the most gifted actor, and when I search my/their memories I find no trace of earlier exposure to the Concern – or whatever it might be called locally – or preparation for what has happened.