"He was an in-patient at the hospital when I first met him, miserably
ill and broken, a victim of poverty and undeserved misfortune. I gave
him one or two little jobs, and when I found what class of man he was I
took him permanently into my service. He is perfectly devoted to me, and
his gratitude is as boundless as it is uncalled for."

"What are the photographs he was referring to?" I asked.

"He is making an enlarged _facsimile_ of one of the thumb-prints on
bromide paper and a negative of the same size in case we want the print
repeated."

"You evidently have some expectation of being able to help poor Hornby,"
said I, "though I cannot imagine how you propose to go to work. To me
his case seems as hopeless a one as it is possible to conceive. One
doesn't like to condemn him, but yet his innocence seems almost
unthinkable."

"It does certainly look like a hopeless case," Thorndyke agreed, "and I
see no way out of it at present. But I make it a rule, in all cases, to
proceed on the strictly classical lines of inductive inquiry--collect
facts, make hypotheses, test them and seek for verification. And I
always endeavour to keep a perfectly open mind.

"Now, in the present case, assuming, as we must, that the robbery has
actually taken place, there are four conceivable hypotheses: (1) that
the robbery was committed by Reuben Hornby; (2) that it was committed by
Walter Hornby; (3) that it was committed by John Hornby, or (4) that it
was committed by some other person or persons.