At first my mind tried to slide the new language sideways into its niche for Arabic, a tongue I had learnt under similar circumstances five years earlier, but by the end of the afternoon, it had grudgingly begun to compile a separate store-house of nouns and verbs in a niche labelled Hindi. With concentrated (that is, around-the-clock) effort, the rudimentaries of most languages can be grasped in a week or two, with childish phrases and a continual “Pardon me?” giving way to slow, stilted fluency a week later. By the end of four weeks, under Holmes’ tutelage, I had no doubt that my somewhat bruised brain would be dreaming in its newest tongue. And it went without saying, my accent would be identical to his, that is, negligible. By the time we landed in Bombay, I would be able to pass for a genial idiot; another fortnight, and I would merely sound stupid.

However, it seemed that Hindustani was not the only subject Holmes had in mind. When our plates were clean and I had satisfactorily recited the nouns and articles for all the objects on the tray, he swept the leavings to one side and laid a pair of tea-spoons and a linen napkin onto the table between us, and began a demonstration of sleight-of-hand.

Under the command of those long, thin, infinitely clever fingers, the silver came alive. It vanished and reappeared in unlikely places; it multiplied, shrank, changed shape, became near liquid, and finally sat quietly where it had begun. I knew his tricks—basic conjuring was a skill I’d begun to learn early in our relationship—but my young fingers had been no match for his. Still, I’d spent one summer conjuring with coins so, although the spoons were more difficult to palm and vanish, my grip was accustomed to the motions. Now I picked up one of the spoons and performed a few of his moves back to him, albeit more slowly and clumsily, and leaving out the multiplication trick since he had stashed the other spoons somewhere about his person. He looked on critically, grunted his approval, and produced the spare silver from an inner pocket.

I had been many things as first the apprentice, then the partner of Sherlock Holmes: gipsy fortune-teller in Wales, personal secretary to a misogynist colonel, Bedu Arab wandering the Palestinian desert, working girl, matron, and Sweet Young Thing. Now, we were going to India, where I supposed I might be asked to dance in a harem or take up a position on the street among the lepers. Or perform conjuring tricks.

“We’re to be Hindu magicians?” I asked.

“As Dr Johnson said, ‘All wonder is the effect of novelty on ignorance.’ And as fire-breathing bears the hazards of flaming beards or self-poisoning with phosphorus or brimstone, and the more spectacular conjuring depends on equipment too heft for easy transport, we shall concentrate on prestidigitation.”

“But why?”