"Now he has rose up standing, and is putting his clues together on his left fingers with his right finger. See? he touches the forefinger--now middle finger--now ring-finger--"
     "Stuck!"
     "Look at him scowl! He can't seem to make out that clue. So he--"
     "See him smile!--like a tiger--and tally off the other fingers like nothing! He's got it, boys; he's got it sure!"
     "Well, I should say! I'd hate to be in that man's place that he's after."

Later, Holmes sums up the case, using his famous "method":

     When quiet fell, Mr. Holmes resumed:
     "We perceive, then, that three facts are established, to wit: the assassin was approximately light-witted; he was not a stranger; his motive was robbery, not revenge. Let us proceed. I hold in my hand a small fragment of fuse, with the recent smell of fire upon it. What is its testimony? Taken with the corroborative evidence of the quartz, it reveals to us that the assassin was a miner. What does it tell us further? This, gentlemen: that the assassination was consummated by means of an explosive. What else does it say? This: that the explosive was located against the side of the cabin nearest the road--the front side--for within six feet of that spot I found it.
     "I hold in my fingers a burnt Swedish match--the kind one rubs on a safety-box. I found it in the road, six hundred and twenty-two feet from the abolished cabin. What does it say? This: that the train was fired from that point. What further does it tell us? This: that the assassin was left-handed. How do I know this? I should not be able to explain to you, gentlemen, how I know it, the signs being so subtle that only long experience and deep study can enable one to detect them. But the signs are here, and they are reinforced by a fact which you must have often noticed in the great detective narratives--that all assassins are left-handed."
     "By Jackson, that's so." said Ham Sandwich, bringing his great hand down with a resounding slap upon his thigh; "blamed if I ever thought of it before."
     "Nor I!" "Nor I!" cried several. "Oh, there can't anything escape him—look at his eye!"

Twain's Holmes accuses the wrong man. Worse, the murder was committed right under Holmes's nose, and he was set up by the murderer to serve as an alibi. After Holmes pronounces his verdict, Stillman, the hound-man, proves him wrong point by point, parodying some of Holmes's words to Watson over Dr. Mortimer's walking stick at the beginning of Hound.

     "The criminal is present, I believe. I will show him to you before long, in case I am right in my guess. Now I will tell you all about the tragedy, from start to finish. The motive wasn't robbery; it was revenge. The murderer wasn't light-witted. He didn't stand six hundred and twenty-two feet away. He didn't get hit with a piece of wood. He didn't place the explosive against the cabin. He didn't bring a shot-bag with him, and he wasn't left-handed. With the exception of these errors, the distinguished guest's statement of the case is substantially correct."

The full text of Twain's story is readily available on line.