“Well, you know, after a crime of this sort we are very careful to keep things in their position. Nothing has been moved. Officer in charge here day and night. This morning, as the man was buried and the investigation over—so far as this room is concerned—we thought we could tidy up a bit. This carpet. You see, it is not fastened down, only just laid there. We had occasion to raise it. We found——”
“Yes? You found——”
Holmes’s face grew tense with anxiety.
“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.”