"The last hypothesis I propose to disregard for the present and confine
myself to the examination of the other three."

"You don't think it possible that Mr. Hornby could have stolen the
diamonds out of his own safe?" I exclaimed.

"I incline at present to no one theory of the matter," replied
Thorndyke. "I merely state the hypotheses. John Hornby had access to the
diamonds, therefore it is possible that he stole them."

"But surely he was responsible to the owners."

"Not in the absence of gross negligence, which the owners would have
difficulty in proving. You see, he was what is called a gratuitous
bailee, and in such a case no responsibility for loss lies with the
bailee unless there has been gross negligence."

"But the thumb-mark, my dear fellow!" I exclaimed. "How can you possibly
get over that?"

"I don't know that I can," answered Thorndyke calmly; "but I see you are
taking the same view as the police, who persist in regarding a
finger-print as a kind of magical touchstone, a final proof, beyond
which inquiry need not go. Now, this is an entire mistake. A
finger-print is merely a fact--a very important and significant one, I
admit--but still a fact, which, like any other fact, requires to be
weighed and measured with reference to its evidential value."

"And what do you propose to do first?" "I shall first satisfy myself