‘No, it was the candle on the side-table that told me. Pray resume your seat and let me know how I can serve you.’

‘My name is Doctor Percy Trevelyan,’ said our visitor, ‘and I live at 403, Brook Street.’

‘Are you not the author of a monograph upon obscure nervous lesions?’ I asked.

His pale cheeks flushed with pleasure at hearing that his work was known to me.

‘I so seldom hear of the work that I thought it was quite dead,’ said he. ‘My publishers give me a most discouraging account of its sale. You are yourself, I presume, a medical man?’

‘A retired Army surgeon.’

‘My own hobby has always been nervous disease. I should wish to make it an absolute specialty, but, of course, a man must take what he can get at first. This, however, is beside the question, Mr Sherlock Holmes, and I quite appreciate how valuable your time is. The fact is that a very singular train of events has occurred recently at my house in Brook Street, and to-night they came to such a head that I felt it was quite impossible for me to wait another hour before asking for your advice and assistance.’

Sherlock Holmes sat down and lit his pipe. ‘You are very welcome to both,’ said he. ‘Pray let me have a detailed account of what the circumstances are which have disturbed you.’

‘One or two of them are so trivial,’ said Dr Trevelyan, ‘that really I am almost ashamed to mention them. But the matter is so inexplicable, and the recent turn which it has taken is so elaborate, that I shall lay it all before you, and you shall judge what is essential and what is not.

‘I am compelled, to begin with, to say something of my own college career. I am a London University man, you know, and I am sure you will not think that I am unduly singing my own praises if I say that my student career was considered by my professors to be a very promising one. After I had graduated I continued to devote myself to research, occupying a minor position in King’s College Hospital, and I was fortunate enough to excite considerable interest by my research into the pathology of catalepsy, and finally to win the Bruce Pinkerton prize and medal by the monograph on nervous lesions to which your friend has just alluded. I should not go too far if I were to say that there was a general impression at that time that a distinguished career lay before me.

‘But the one great stumbling-block lay in my want of capital. As you will readily understand, a specialist who aims high is compelled to start in one of a dozen streets in the Cavendish Square quarter, all of which entail enormous rents and furnishing expenses. Besides this preliminary out-lay, he must be prepared to keep himself for some years, and to hire a presentable carriage and horse. To do this was quite beyond my power, and I could only hope that by economy I might in ten years’ time save enough to enable me to put up my plate. Suddenly, however, an unexpected incident opened up quite a new prospect to me.

‘This was a visit from a gentleman of the name of Blessington, who was a complete stranger to me. He came up into my room one morning, and plunged into business in an instant.

“‘You are the same Percy Trevelyan who has had so distinguished a career and won a great prize lately?’ said he. I bowed.

“‘Answer me frankly,” he continued, “for you will find it to your interest to do so. You have all the cleverness which makes a successful man. Have you the tact?”

‘I could not help smiling at the abruptness of the question.

‘ “I trust that I have my share,” I said.