"As to Walter Hornby, he may have had the means of obtaining Reuben's
thumb-mark; but there is no evidence that he had access either to the
diamonds or to Mr. Hornby's memorandum block. The _prima facie_
probabilities in his case, therefore, are very slight."

"The actual points at issue, then," I said, "are, whether Reuben had any
means of opening the safe, and whether Mr. Hornby ever did actually have
the opportunity of obtaining Reuben's thumb-mark in blood on his
memorandum block."

"Yes," replied Thorndyke. "Those are the points--with some others--and
they are likely to remain unsettled. Reuben's rooms have been searched
by the police, who failed to find any skeleton or duplicate keys; but
this proves nothing, as he would probably have made away with them when
he heard of the thumb-mark being found. As to the other matter, I have
asked Reuben, and he has no recollection of ever having made a
thumb-mark in blood. So there the matter rests."

"And what about Mr. Hornby's liability for the diamonds?"

"I think we may dismiss that," answered Thorndyke. "He had undertaken no
liability and there was no negligence. He would not be liable at law."

After my colleague retired, which he did quite early, I sat for a long
time pondering upon this singular case in which I found myself involved.
And the more I thought about it the more puzzled I became. If Thorndyke
had no more satisfactory explanation to offer than that which he had
given me this evening, the defence was hopeless, for the court was not
likely to accept his estimate of the evidential value of finger-prints.