Presently, however, I found that he had many acquaintances, and those in the most different classes of society. There was one little sallow rat-faced, dark-eyed fellow who was introduced to me as Mr. Lestrade, and who came three or four times in a single week. One morning a young girl called, fashionably dressed, and stayed for half an hour or more. The same afternoon brought a grey-headed, seedy visitor, looking like a Jew pedlar, who appeared to me to be much excited, and who was closely followed by a slip-shod elderly woman. On another occasion an old white-haired gentleman had an interview with my companion; and on another a railway porter in his velveteen uniform. When any of these nondescript individuals put in an appearance, Sherlock Holmes used to beg for the use of the sitting-room, and I would retire to my bed-room. He always apologised to me for putting me to this inconvenience. "I have to use this room as a place of business," he said, "and these people are my clients." Again I had an opportunity of asking him a point blank question, and again my delicacy prevented me from forcing another man to confide in me. I imagined at the time that he had some strong reason for not alluding to it, but he soon dispelled the idea by coming round to the subject of his own accord.
(from "A Study in Scarlet"

"Yes, I have a turn both for observation and for deduction. The theories which I have expressed there, and which appear to you to be so chimerical are really extremely practical—so practical that I depend upon them for my bread and cheese." "And how?" I asked involuntarily. "Well, I have a trade of my own. I suppose I am the only one in the world. I'm a consulting detective, if you can understand what that is. Here in London we have lots of Government detectives and lots of private ones. When these fellows are at fault they come to me, and I manage to put them on the right scent. They lay all the evidence before me, and I am generally able, by the help of my knowledge of the history of crime, to set them straight. There is a strong family resemblance about misdeeds, and if you have all the details of a thousand at your finger ends, it is odd if you can't unravel the thousand and first. Lestrade is a well-known detective. He got himself into a fog recently over a forgery case, and that was what brought him here."
(from "A Study in Scarlet")

MY DEAR MR. SHERLOCK HOLMES,
There has been a bad business during the night at 3, Lauriston Gardens, off the Brixton Road. Our man on the beat saw a light there about two in the morning, and as the house was an empty one, suspected that something was amiss. He found the door open, and in the front room, which is bare of furniture, discovered the body of a gentleman, well dressed, and having cards in his pocket bearing the name of 'Enoch J. Drebber, Cleveland, Ohio, U.S.A.' There had been no robbery, nor is there any evidence as to how the man met his death. There are marks of blood in the room, but there is no wound upon his person. We are at a loss as to how he came into the empty house; indeed, the whole affair is a puzzler. If you can come round to the house any time before twelve, you will find me there. I have left everything in statu quo until I hear from you. If you are unable to come I shall give you fuller details, and would esteem it a great kindness if you would favour me with your opinion.
Yours faithfully,

TOBIAS GREGSON."

I spent the whole of yesterday evening in making enquiries entirely without avail. This morning I began very early, and at eight o'clock I reached Halliday's Private Hotel, in Little George Street. On my enquiry as to whether a Mr. Stangerson was living there, they at once answered me in the affirmative. "'No doubt you are the gentleman whom he was expecting,' they said. 'He has been waiting for a gentleman for two days.' "'Where is he now?' I asked. "'He is upstairs in bed. He wished to be called at nine.' "'I will go up and see him at once,' I said. "It seemed to me that my sudden appearance might shake his nerves and lead him to say something unguarded. The Boots volunteered to show me the room: it was on the second floor, and there was a small corridor leading up to it. The Boots pointed out the door to me, and was about to go downstairs again when I saw something that made me feel sickish, in spite of my twenty years' experience. From under the door there curled a little red ribbon of blood, which had meandered across the passage and formed a little pool along the skirting at the other side. I gave a cry, which brought the Boots back. He nearly fainted when he saw it. The door was locked on the inside, but we put our shoulders to it, and knocked it in. The window of the room was open, and beside the window, all huddled up, lay the body of a man in his nightdress. He was quite dead, and had been for some time, for his limbs were rigid and cold. When we turned him over, the Boots recognised him at once as being the same gentleman who had engaged the room under the name of Joseph Stangerson. The cause of death was a deep stab in the left side, which must have penetrated the heart. And now comes the strangest part of the affair. What do you suppose was above the murdered man?"
I felt a creeping of the flesh, and a presentiment of coming horror, even before Sherlock Holmes answered. "The word Rache, written in letters of blood," he said. "That was it," said Lestrade, in an awe-struck voice; and we were all silent for a while.