“Well, I’m sure you would never guess in a hundred years what we did find. You see that stain on the carpet? Well, a great deal must have soaked through, must it not?”
“Undoubtedly it must.”
“Well, you will be surprised to hear that there is no stain on the white woodwork to correspond.”
“No stain! But there must—”
“Yes, so you would say. But the fact remains that there isn’t.”
He took the corner of the carpet in his hand and, turning it over, he showed that it was indeed as he said.
“But the under side is as stained as the upper. It must have left a mark.”
Lestrade chuckled with delight at having puzzled the famous expert.
“Now, I’ll show you the explanation. There is a second stain, but it does not correspond with the other. See for yourself.” As he spoke he turned over another portion of the carpet, and there, sure enough, was a great crimson spill upon the square white facing of the old-fashioned floor. “What do you make of that, Mr. Holmes?”
“Why, it is simple enough. The two stains did correspond, but the carpet has been turned round. As it was square and unfastened it was easily done.”
“The official police don’t need you, Mr. Holmes, to tell them that the carpet must have been turned round. That’s clear enough, for the stains lie above each other—if you lay it over this way. But what I want to know is, who shifted the carpet, and why?”