"Then there’s your brother. Your phone. It’s expensive - email enabled, MP3 player. If you’re looking for a flat share you wouldn’t waste money on this. It’s a gift, then. Scratches: Not one, many over time. It’s been in the same pocket as keys and coins. A man sitting next to me doesn’t treat his one luxury item like this. So, it’s had a previous owner. Next bit’s easy. You know it already."
"Harry Watson. Clearly a family member who’s given you his old phone. Not your father. This is a young man’s gadget. Could be a cousin, but you’re a war hero who can’t find a place to live. Unlikely you’ve got an extended family, certainly not one you’re close to. So, brother it is."
"Now Clara. Who’s Clara? Three kisses says it’s a romantic attachment. Expense of the phone says wife, not girlfriend. She must have given it to him recently; this model’s only six months old. Marriage in trouble then. Six months on and he’s just giving it away? If she’d left him, he would have kept it. People do. Sentiment. No, he wanted rid of it. He left her."
"He gave the phone to you. That says he wants you to stay in touch. You’re looking for cheap accommodation and you’re not going to your bother for help. That says you’ve got problems with him. Maybe you liked his wife. Maybe you don’t like his drinking."
"How can you possibly know about the drinking?"
"Shot in the dark. Good one, though. Power connection. Tiny little scuff marks around the edge of it. Every night he goes to plug it in to charge but his hands are shaking. You never see those marks on a sober man’s phone, never see a drunk’s without them."
"I have heard you say that it is difficult for a man to have any object in daily use without leaving the impress of his individuality upon it in such a way that a trained observer might read it. Now, I have here a watch which has recently come into my possession. Would you have the kindness to let me have an opinion upon the character or habits of the late owner?"
I handed him over the watch with some slight feeling of amusement in my heart, for the test was, as I thought, an impossible one, and I intended it as a lesson against the somewhat dogmatic tone which he occasionally assumed. He balanced the watch in his hand, gazed hard at the dial, opened the back, and examined the works, first with his naked eyes and then with a powerful convex lens. I could hardly keep from smiling at his crestfallen face when he finally snapped the case to and handed it back.
"There are hardly any data," he remarked. "The watch has been recently cleaned, which robs me of my most suggestive facts.""You are right," I answered. "It was cleaned before being sent to me." In my heart I accused my companion of putting forward a most lame and impotent excuse to cover his failure. What data could he expect from an uncleaned watch?
"Though unsatisfactory, my research has not been entirely barren," he observed, staring up at the ceiling with dreamy, lack-lustre eyes. "Subject to your correction, I should judge that the watch belonged to your elder brother, who inherited it from your father."
"That you gather, no doubt, from the H. W. upon the back?"
"Quite so. The W. suggests your own name. The date of the watch is nearly fifty years back, and the initials are as old as the watch: so it was made for the last generation. Jewelry usually descends to the eldest son, and he is most likely to have the same name as the father. Your father has, if I remember right, been dead many years. It has, therefore, been in the hands of your eldest brother."
"Right, so far," said I. "Anything else?"
"He was a man of untidy habits,—very untidy and careless. He was left with good prospects, but he threw away his chances, lived for some time in poverty with occasional short intervals of prosperity, and finally, taking to drink, he died. That is all I can gather."
I sprang from my chair and limped impatiently about the room with considerable bitterness in my heart.
"This is unworthy of you, Holmes," I said. "I could not have believed that you would have descended to this. You have made inquires into the history of my unhappy brother, and you now pretend to deduce this knowledge in some fanciful way. You cannot expect me to believe that you have read all this from his old watch! It is unkind, and, to speak plainly, has a touch of charlatanism in it."
"My dear doctor," said he, kindly, "pray accept my apologies. Viewing the matter as an abstract problem, I had forgotten how personal and painful a thing it might be to you. I assure you, however, that I never even knew that you had a brother until you handed me the watch."
"Then how in the name of all that is wonderful did you get these facts? They are absolutely correct in every particular."
"Ah, that is good luck. I could only say what was the balance of probability. I did not at all expect to be so accurate."
"But it was not mere guess-work?"
"No, no: I never guess. It is a shocking habit,—destructive to the logical faculty. What seems strange to you is only so because you do not follow my train of thought or observe the small facts upon which large inferences may depend. For example, I began by stating that your brother was careless. When you observe the lower part of that watch-case you notice that it is not only dinted in two places, but it is cut and marked all over from the habit of keeping other hard objects, such as coins or keys, in the same pocket. Surely it is no great feat to assume that a man who treats a fifty-guinea watch so cavalierly must be a careless man. Neither is it a very far-fetched inference that a man who inherits one article of such value is pretty well provided for in other respects."
I nodded, to show that I followed his reasoning.
"It is very customary for pawnbrokers in England, when they take a watch, to scratch the number of the ticket with a pin-point upon the inside of the case. It is more handy than a label, as there is no risk of the number being lost or transposed. There are no less than four such numbers visible to my lens on the inside of this case. Inference,—that your brother was often at low water. Secondary inference,—that he had occasional bursts of prosperity, or he could not have redeemed the pledge. Finally, I ask you to look at the inner plate, which contains the key-hole. Look at the thousands of scratches all round the hole,—marks where the key has slipped. What sober man’s key could have scored those grooves? But you will never see a drunkard’s watch without them. He winds it at night, and he leaves these traces of his unsteady hand. Where is the mystery in all this?"- The Sign of Four, Chapter 2