Depend upon it there is nothing so unnatural as the commonplace.’

I smiled and shook my head. ‘I can quite understand you thinking so,’ I said. ‘Of course, in your position of unofficial adviser and helper to everybody who is absolutely puzzled, throughout three continents, you are brought in contact with all that is strange and bizarre. But here’—I picked up the morning paper from the ground—‘let us put it to a practical test. Here is the first heading upon which I come. “A husband’s cruelty to his wife.” There is half a column of print, but I know without reading it that it is all perfectly familiar to me. There is, of course, the other woman, the drink, the push, the blow, the bruise, the sympathetic sister or landlady. The crudest of writers could invent nothing more crude.’

‘Indeed, your example is an unfortunate one for your argument,’ said Holmes, taking the paper, and glancing his eye down it. ‘This is the Dundas separation case, and, as it happens, I was engaged in clearing up some small points in connection with it. The husband was a teetotaller, there was no other woman, and the conduct complained of was that he had drifted into the habit of winding up every meal by taking out his false teeth and hurling them at his wife, which you will allow is not an action likely to occur to the imagination of the average story-teller. Take a pinch of snuff, Doctor, and acknowledge that I have scored over you in your example.’

He held out his snuff-box of old gold, with a great amethyst in the centre of the lid. Its splendour was in such contrast to his homely ways and simple life that I could not help commenting upon it.

‘Ah,’ said he, ‘I forgot that I had not seen you for some weeks. It is a little souvenir from the King of Bohemia in return for my assistance in the case of the Irene Adler papers.’

‘And the ring?’ I asked, glancing at a remarkable brilliant which sparkled upon his finger.

‘It was from the reigning family of Holland, though the matter in which I served them was of such delicacy that I cannot confide it even to you, who have been good enough to chronicle one or two of my little problems.’

‘And have you any on hand just now?’ I asked with interest.

‘Some ten or twelve, but none which presents any feature of interest. They are important, you understand, without being interesting. Indeed, I have found that it is usually in unimportant matters that there is a field for observation, and for the quick analysis of cause and effect which gives the charm to an investigation. The larger crimes are apt to be the simpler, for the bigger the crime, the more obvious, as a rule, is the motive. In these cases, save for one rather intricate matter which has been referred to me from Marseilles, there is nothing which presents any features of interest. It is possible, however, that I may have something better before very many minutes are over, for this is one of my clients, or I am much mistaken.’

He had risen from his chair, and was standing between the parted blinds, gazing down into the dull, neutral-tinted London street. Looking over his shoulder I saw that on the pavement opposite there stood a large woman with a heavy fur boa round her neck, and a large curling red feather in a broad-brimmed hat which was tilted in a coquettish Duchess-of-Devonshire fashion over her ear. From under this great panoply she peeped up in a nervous, hesitating fashion at our windows, while her body oscillated backwards and forwards, and her fingers fidgeted with her glove buttons. Suddenly, with a plunge, as of the swimmer who leaves the bank, she hurried across the road, and we heard the sharp clang of the bell.

‘I have seen those symptoms before,’ said Holmes, throwing his cigarette into the fire. ‘Oscillation upon the pavement always means an affaire du coeur. She would like advice, but is not sure that the matter is not too delicate for communication. And yet even here we may discriminate. When a woman has been seriously wronged by a man she no longer oscillates, and the usual symptom is a broken bell wire. Here we may take it that there is a love matter, but that the maiden is not so much angry as perplexed, or grieved. But here she comes in person to resolve our doubts.’

As he spoke there was a tap at the door, and the boy in buttons entered to announce Miss Mary Sutherland, while the lady herself loomed behind his small black figure like a full-sailed merchantman behind a tiny pilot boat. Sherlock Holmes welcomed her with the easy courtesy for which he was remarkable, and having closed the door, and bowed her into an armchair, he looked over her in the minute and yet abstracted fashion which was peculiar to him.

‘Do you not find,’ he said, ‘that with your short sight it is a little trying to do so much typewriting?’

‘I did at first,’ she answered, ‘but now I know where the letters are without looking.’ Then, suddenly realizing the full purport of his words, she gave a violent start, and looked up with fear and astonishment upon her broad, good-humoured face. ‘You’ve heard about me, Mr Holmes,’ she cried, ‘else how could you know all that?’

‘Never mind,’ said Holmes, laughing, ‘it is my business to know things. Perhaps I have trained myself to see what others overlook.