we will take an impression in blood."
The thumb was accordingly cleansed and dried afresh, when Thorndyke, having pricked his own thumb with a needle, squeezed out a good-sized drop of blood on to a card.
"There," said he, with a smile, as he spread the drop out with the needle into a little shallow pool, "it is not every lawyer who is willing to shed his blood in the interests of his client."
He proceeded to make a dozen prints as before on two cards, writing a number with his pencil opposite each print as he made it.
"We are now," said he, as he finally cleansed his client's thumb, "furnished with the material for a preliminary investigation, and if you will now give me your address, Mr. Hornby, we may consider our business concluded for the present. I must apologise to you, Mr. Lawley, for having detained you so long with these experiments."
The lawyer had, in fact, been viewing the proceedings with hardly concealed impatience, and he now rose with evident relief that they were at an end.
"I have been highly interested," he said mendaciously, "though I confess I do not quite fathom your intentions. And, by the way, I should like to have a few words with you on another matter, if Mr. Reuben would not mind waiting for me in the square just a few minutes."
"Not at all," said Reuben, who was, I perceived, in no way deceived by the lawyer's pretence. "Don't hurry on my account; my time is my own—at present." He held out his hand to Thorndyke, who grasped it cordially.
"Good-bye, Mr. Hornby," said the latter. "Do not be unreasonably sanguine, but at the same time, do not lose heart. Keep your wits about you and let me know at once if anything occurs to you that may have a bearing on the case."
The young man then took his leave, and, as the door closed after him, Mr. Lawley turned towards Thorndyke.
"I thought I had better have a word with you alone," he said, "just to hear what line you propose to take up, for I confess that your attitude has puzzled me completely."
"What line would you propose?" asked Thorndyke.
"Well," said the lawyer, with a shrug of his shoulders, "the position seems to be this: our young friend has stolen a parcel of diamonds and has been found out; at least, that is how the matter presents itself to me."
"That is not how it presents itself to me," said Thorndyke drily. "He may have taken the diamonds or he may not. I have no means of judging until I have sifted the evidence and acquired a few more facts. This I hope to do in the course of the next day or two, and I suggest that we postpone the consideration of our plan of campaign until I have seen what line of defence it is possible to adopt."
"As you will," replied the lawyer, taking up his hat, "but I am afraid you are encouraging the young rogue to entertain hopes that will only make his fall the harder—to say nothing of our own position. We don't want to make ourselves ridiculous in court, you know."
"I don't, certainly," agreed Thorndyke. "However, I will look into the matter and communicate with you in the course of a day or two."
He stood holding the door open as the lawyer descended the stairs, and when the footsteps at length died away, he closed it sharply and turned to me with an air of annoyance.
"The 'young rogue,'" he remarked, "does not appear to me to have been very happy in his choice of a solicitor. By the way, Jervis, I understand you are out of employment just now?"
"That is so," I answered.
"Would you care to help me—as a matter of business, of course—to work up this case? I have a lot of other work on hand and your assistance would be of great value to me."
I said, with great truth, that I should be delighted.
"Then," said Thorndyke, "come round to breakfast to-morrow and we will settle the terms, and you can commence your duties at once. And now let us light our pipes and finish our yarns as though agitated clients and thick-headed solicitors had no existence."
A Lady in the Case
When I arrived at Thorndyke's chambers on the following morning, I found my friend already hard at work. Breakfast was laid at one end of the table, while at the other stood a microscope of the pattern used for examining plate-cultures of micro-organisms, on the wide stage of which was one of the cards bearing six thumb-prints in blood. A condenser threw a bright spot of light on the card, which Thorndyke had been examining when I knocked, as I gathered from the position of the chair, which he now pushed back against the wall.
"I see you have commenced work on our problem," I remarked as, in response to a double ring of the electric bell, Polton entered with the materials for our repast.
"Yes," answered Thorndyke. "I have opened the campaign, supported, as usual, by my trusty chief-of-staff; eh! Polton?"
The little man, whose intellectual, refined countenance and dignified bearing seemed oddly out of character with the tea-tray that he carried, smiled proudly, and, with a glance of affectionate admiration at my friend, replied—
"Yes, sir. We haven't been letting the grass grow under our feet. There's a beautiful negative washing upstairs and a bromide enlargement too, which will be mounted and dried by the time you have finished your breakfast."
"A wonderful man that, Jervis," my friend observed as his assistant retired. "Looks like a rural dean or a chancery judge, and was obviously intended by Nature to be a professor of physics. As an actual fact he was first a watchmaker, then a maker of optical instruments, and now he is mechanical factotum to a medical jurist. He is my right-hand, is Polton; takes an idea before you have time to utter it—but you will make his more intimate acquaintance by-and-by."
"Where did you pick him up?" I asked.
"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
