t it was John McFarlane who did this crime."

He led us through the passage and out into a dark hall beyond.

"This is where young McFarlane must have come out to get his hat
after the crime was done," said he. "Now, look at this." With dramatic
suddenness he struck a match and by its light exposed a stain of blood
upon the whitewashed wall. As he held the match nearer I saw that it was
more than a stain. It was the well-marked print of a thumb.

"Look at that with your magnifying glass, Mr. Holmes."

"Yes, I am doing so."

"You are aware that no two thumb marks are alike?"

"I have heard something of the kind."

"Well, then, will you please compare that print with this wax impression
of young McFarlane's right thumb, taken by my orders this morning?"

As he held the waxen print close to the blood-stain it did not take
a magnifying glass to see that the two were undoubtedly from the same
thumb. It was evident to me that our unfortunate client was lost.

"That is final," said Lestrade.

"Yes, that is final," I involuntarily echoed.

"It is final," said Holmes.

Something in his tone caught my ear, and I turned to look at him. An
extraordinary change had come over his face. It was writhing with inward
merriment. His two eyes were shining like stars. It seemed to me that
he was making desperate efforts to restrain a convulsive attack of
laughter.

"Dear me! Dear me!" he said at last. "Well, now, who would have thought
it? And how deceptive appearances may be, to be sure! Such a nice young
man to look at! It is a lesson to us not to trust our own judgment, is
it not, Lestrade?"

"Yes, some of us are a little too much inclined to be cocksure, Mr.
Holmes," said Lestrade. The man's insolence was maddening, but we could
not resent it.

"What a providential thing that this young man should press his right
thumb against the wall in taking his hat from the peg! Such a very
natural action, too, if you come to think of it." Holmes was outwardly
calm, but his whole body gave a wriggle of suppressed excitement as he
spoke. "By the way, Lestrade, who made this remarkable discovery?"

"It was the housekeeper, Mrs. Lexington, who drew the night constable's
attention to it."

"Where was the night constable?"

"He remained on guard in the bedroom where the crime was committed, so
as to see that nothing was touched."

"But why didn't the police see this mark yesterday?"

"Well, we had no particular reason to make a