‘I will lock it for you in a special box which I construct for the purpose,’ Lossop continued, ‘hang it on this wall, and I guarantee there is no locksmith alive who can open it but me.’

‘But … why?’ I asked, frankly amazed. ‘And more to the point, how can you afford to live, paid in such a manner?’

‘Banks, Watson,’ said Holmes. ‘The banks pay him handsomely for custom, unassailable locks. And there are other clients, not all of whom are legitimate businesses. Am I not right, Mr Lossop?’

Lossop’s answer was the briefest smile. I shook my head, unconvinced.

‘But why—?’ I began.

‘These are trophies, Watson.’

‘What do you do with these things? Extort people?’ I could not stop myself.

‘No,’ said Lossop. ‘I … treasure them. I take them out upon occasion and ruminate on their value to the depositor. I revel in the human story. You see, I have few stories of my own. You might say I live vicariously. Oh, I see you don’t understand. They offer a kind of sustenance.’ He laughed, an unhealthy, percussive sound like a dry cough. ‘Does that make it any clearer?’

I suddenly saw this strange, oleaginous little man as a kind of enchanted toad, hiding under a rock and picking over sparkling valuables stolen from people who had wandered too near – feeding on them. I was revolted.

But I looked down at the box in my hands. I had to discover what was inside it. I had to know what my mother had left for me. I did not trust Lossop but felt I had no choice.

‘I … I don’t know what I have to give you that would serve,’ I said. ‘Something I have kept and treasure? I don’t know. Perhaps the charm off my brother’s watch? No? The watch itself?’

Lossop shook his head.

‘I believe I have … my childhood wooden soldiers, one or two … somewhere – er, a little clock, ticket stubs to the circus in 1860; my first stethoscope?’ I had a vague recollection of something like these in a trunk in the attic at 221B. Lossop stared at me. ‘I have a favourite hat?’

That laugh again. ‘Dear Doctor, you are infinitely – what is the word – ordinary.’ Lossop turned to stare at Holmes, who remained silent. ‘But you have something. I know a man with secrets when I see one. What will you give me?’

Holmes, without taking his eyes off the man, reached into the inside pocket of his coat and removed a small brown envelope.

‘You came prepared, Mr Sherlock Holmes,’ said Lossop.

‘I did indeed. I had heard of your collection.’

‘Then why ask my price?’

‘I was hoping money would suffice.’

Lossop stared at the envelope. He licked his lips.

‘But clearly not,’ said Holmes. ‘Here is … here is a photograph.’