ned--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."

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?"

I could see from Holmes's rigid face that he was vibrating with inward
excitement.

"Look here, Lestrade," said he, "has that constable in the passage been
in charge of the place all the time?"

"Yes, he has."

"Well, take my advice. Examine him carefully. Don't do it before us.
Well wait here. You take him into the back room. You'll be more likely
to get a confession out of him alone. Ask him how he dared to admit
people and leave them alone in this room. Don't ask him if he has done
it. Take it for granted. Tell him you KNOW someone has been here. Press
him. Tell him that a full confession is his only chance of forgiveness.
Do exactly what I tell you!"

"By George, if he knows I'll have it out of him!" cried Lestrade. He
darted into the hall, and a few moments later his bullying voice sounded
from the back room.

"Now, Watson,