As he spoke, he whipped a tape measure and a large round magnifying glass from his pocket. With these two implements he trotted noiselessly about the room, sometimes stopping, occasionally kneeling, and once lying flat upon his face. So engrossed was he with his occupation that he appeared to have forgotten our presence, for he chattered away to himself under his breath the whole time, keeping up a running fire of exclamations, groans, whistles, and little cries suggestive of encouragement and of hope. As I watched him I was irresistibly reminded of a pure-blooded well-trained foxhound as it dashes backwards and forwards through the covert, whining in its eagerness, until it comes across the lost scent. For twenty minutes or more he continued his researches, measuring with the most exact care the distance between marks which were entirely invisible to me, and occasionally applying his tape to the walls in an equally incomprehensible manner. In one place he gathered up very carefully a little pile of grey dust from the floor, and packed it away in an envelope. Finally, he examined with his glass the word upon the wall, going over every letter of it with the most minute exactness. This done, he appeared to be satisfied, for he replaced his tape and his glass in his pocket.

“They say that genius is an infinite capacity for taking pains,” he remarked with a smile. “It’s a very bad definition, but it does apply to detective work.”

Gregson and Lestrade had watched the manœuvres of their amateur companion with considerable curiosity and some contempt. They evidently failed to appreciate the fact, which I had begun to realize, that Sherlock Holmes’ smallest actions were all directed towards some definite and practical end.

“What do you think of it, sir?” they both asked.

“It would be robbing you of the credit of the case if I was to presume to help you,” remarked my friend. “You are doing so well now that it would be a pity for anyone to interfere.” There was a world of sarcasm in his voice as he spoke. “If you will let me know how your investigations go,” he continued, “I shall be happy to give you any help I can. In the meantime I should like to speak to the constable who found the body. Can you give me his name and address?”

Lestrade glanced at his note-book. “John Rance,” he said. “He is off duty now. You will find him at 46, Audley Court, Kennington Park Gate.”

Holmes took a note of the address.