She smiled back, accepting the challenge, and clapped her hands.

'Maria!' she called out. 'Please show Mr Stone the apartment.'

'So you can bear to have me in your house? I am flattered,' I said.

'You should be. But you have the aura of an honest man, a good man,' she replied seriously.

'I beg your pardon?'

'Your aura. It radiates around you, revealing the nature of the spirit which animates the machinery of your body. Yours is gentle, blue and yellow. You are divided in spirit, between the desire for peace and for adventure. For power and for tranquillity. You desire much, but I feel that you have a sense of fairness. You are divided between the masculine, and the feminine, but in you the attributes are wrongly apportioned. It is your feminine which is adventurous, the masculine which desires peace. You will have trouble reconciling these, Mr Stone, but they make you interesting.'

She gave the distinct impression that she wanted me in her house so she could study me, like some grotesque entomologist, but she nonetheless had described the battle between my fiery mother and my peaceable father remarkably well. Disconcertingly so, and she saw that I was impressed despite the fact that she was talking nonsense.

The business of packing was delayed by an encounter I had in the hotel on my return. As I walked into the lobby and asked for my key, I noticed a small man get up from his chair, and come towards me.

'My dear Stone!' this person said in a thick Italian accent as he grabbed me by the hand and pulled me round to face him. 'I hardly expected it to be true! Remarkable! I'm so pleased to see you!'

I looked at him blankly for a moment, then it dawned on me who he was. I believe I mentioned that, several years previously, I had tried my hand at dissipation. I am not ashamed of this period of my life, I believe it is inevitable in young men whose energies are not wasted by manual labour, and, as I say, I found that the pleasures of such a life faded quickly and have never returned. I have not spent my older years wondering what it would have been like to have done certain things, nor did I have any temptation in middle age to try and recapture my youth and thus make myself into a laughing stock.

During that period, I made the acquaintance of a group of young men: some were the useless sprigs of nobility well on their way to illness and early death from excess (thus weakening a class of society and fending off the likelihood of revolution, for why trouble to overthrow people who are doing such a good job of rendering themselves powerless?); some were simple idlers spending an inheritance pretending to be poets or painters; and a couple were medical students, who had a wildness of such severity that I would hesitate ever to place myself under their care. One of these, however, is now a personal physician to His Majesty, which goes to show that even the greatest sinners are capable of redemption. Of the others, one became a high court judge and one shot himself in the aftermath of the Dunbury scandal, a foolishly conceived scheme to dun the public by proposing vast profits from a railway built across a two-hundred-mile swamp in Russia. My friend, a man for whom I continued to have affection to the end, went vastly into debt to buy shares in the hope of recovering a dire financial situation, and was ruined.

The man who now greeted me was one of the medical students. I never paid him much attention and never even knew his name – something foreign, I knew, but everyone always called him Joe, a nickname more insulting than friendly, for it assumed an informality more suited to a pet or native bearer than an equal.

Joe – or Dottore Giuseppe Marangoni, as he was now called – had changed over the past few years, that was clear. Previously he had had the sort of personality that could lead you to overlook him entirely; one of those who waited to be spoken to, and appeared grateful to be included in any conversation. Only his eyes suggested there might be something more to him, for he was always watching, always interested. For what purpose never seemed clear.

And this was the person now beaming at me and shaking my hand, leading me to a table in the corner for a chat. It is disconcerting to encounter someone once known, but not seen for several years. At that stage the shock was limited, but still real. Now it is positively a heartache to meet a person I have not seen for thirty or forty years, to see the thinning hair, the stoop, the lines when you expect (no matter how much you realise it cannot be so) the person to look exactly as they did when last seen. And to realise they are as shocked by your appearance as you by theirs.

As we had swapped country, so we also exchanged roles; my surprise at Marangoni's sudden reappearance in my life was so great that I said little. He, in contrast, never stopped talking. We remembered things very differently; he talked of the good fellowship of his days in London, the fine friends he had made, asked about the members of that little group of apprentice rakes – which information I could not provide, as, apart from Campbell, I had cast them off as I had abandoned that way of life, and I have never cared for gossip in any case. Then he began to surprise me.

'I wish I'd liked London more,' he said. 'It is such a dull place.'

'In comparison with Venice?'

He groaned. 'Ah, no. Professionally Venice is interesting, but hardly glittering, alas. No, in comparison to a place like Paris, for example. The English – do forgive me, my friend – are so respectable.'

I was half-minded to be insulted by this, but looked enquiringly instead.

'Take my fellow medical students, for example. In Paris, they live together, and eat together, and all have their shopgirls for mistresses and housekeepers until they qualify or find someone suitable to marry. Their life is their own. In London everyone lives with a landlady, eats every evening some hideous meal she has cooked and goes to church on Sunday. Riotous living consists of getting drunk, and little else.'

'I'm sorry you were disappointed.'

'I wasn't there to enjoy myself; merely to learn and observe. Which I did, with great profit.'

'To learn and observe what?'

'Medicine, as you know. Particularly the science of alienism. I am a doctor of the mind and so it is my business to study people in all their variety. I learned much there, although less than I did in Paris. The group you were attached to was full of instruction.'

I was, as may be imagined, a little offended by this remark; the idea that all the time we were ignoring him, treating him as some insignificant little foreigner, he was, in fact watching and assessing us. A bit like the Marchesa, only more scientific, I hoped. He saw my discomfort and laughed.

'Do not be perturbed. You were the least interesting person there.'

'I do not find that reassuring.'

'But who knows what lurks beneath the surface? I joke. You were by far the most normal of my companions. The others, mind you, were quite fascinating in their many different ways.' He mentioned one man. 'Clear degenerate tendencies, with a pronounced swelling indicating distorted cranial lobes. Certainly a tendency to insanity, erratic judgement and a pronounced attraction to violence.'

'He has just become a Queen's Counsel,' I commented dryly.

'Proves my point, does it not?'

I said nothing. (A few weeks ago, as I write, I discovered my erstwhile acquaintance has been confined to an asylum after a murderous attack on his wife of thirty years. The matter has been kept quiet lest the idea of a complete lunatic in charge of criminal cases – as a judge he became notorious for his infliction of the death penalty – lessens the awful majesty of the law in the public's mind.)

'Alas, I rarely have the opportunity to deal with such intricate cases now,' he said almost wistfully. I was not hugely interested, but asked him of his progress since we had last met. It appeared that Marangoni, his studies in Paris ended, had returned to Milan, where he had briefly worked in an asylum, trying to introduce the best French practices. He had done so well (this was his account, not mine) that he had then been transferred to the Veneto, to embody there the new ideas that unification with Italy represented. He was the emissary of the State, sent to organise the asylums of the city and to corral, bully, persuade and intimidate the insane back to health, using the most up-to-date methods. He was not over-optimistic about his prospects, although gratified by the salary his new employment provided.