"I understand," said I.
"Now this was a case in which you were given the result and had to find everything else for yourself. Now let me endeavour to show you the different steps in my reasoning. To begin at the beginning. I approached the house, as you know, on foot, and with my mind entirely free from all impressions. I naturally began by examining the roadway, and there, as I have already explained to you, I saw clearly the marks of a cab, which, I ascertained by inquiry, must have been there during the night. I satisfied myself that it was a cab and not a private carriage by the narrow gauge of the wheels. The ordinary London growler is considerably less wide than a gentleman's brougham.
"This was the first point gained. I then walked slowly down the garden path, which happened to be composed of a clay soil, peculiarly suitable for taking impressions. No doubt it appeared to you to be a mere trampled line of slush, but to my trained eyes every mark upon its surface had a meaning. There is no branch of detective science which is so important and so much neglected as the art of tracing footsteps. Happily, I have always laid great stress upon it, and much practice has made it second nature to me. I saw the heavy footmarks of the constables, but I saw also the track of the two men who had first passed through the garden. It was easy to tell that they had been before the others, because in places their marks had been entirely obliterated by the others coming upon the top of them. In this way my second link was formed, which told me that the nocturnal visitors were two in number, one remarkable for his height (as I calculated from the length of his stride), and the other fashionably dressed, to judge from the small and elegant impression left by his boots.
"On entering the house this last inference was confirmed. My well-booted man lay before me. The tall one, then, had done the murder, if murder there was. There was no wound upon the dead man's person, but the agitated expression upon his face assured me that he had foreseen his fate before it came upon him. Men who die from heart disease, or any sudden natural cause, never by any chance exhibit agitation upon their features. Having sniffed the dead man's lips I detected a slightly sour smell, and I came to the conclusion that he had had poison forced upon him. Again, I argued that it had been forced upon him from the hatred and fear expressed upon his face. By the method of exclusion, I had arrived at this result, for no other hypothesis would meet the facts. Do not imagine that it was a very unheard of idea. The forcible administration of poison is by no means a new thing in criminal annals. The cases of Dolsky in Odessa, and of Leturier in Montpellier, will occur at once to any toxicologist.