"This is very interesting and important," he said, when I had finished; "really, Jervis, you are a most invaluable coadjutor. It seems that information, which would be strictly withheld from the forbidding Jorkins, trickles freely and unasked into the ear of the genial Spenlow. Now, I suppose you regard your hypothesis as having received very substantial confirmation?"

"Certainly, I do."

"And very justifiably. You see now how completely you were in the right when you allowed yourself to entertain this theory of the crime in spite of its apparent improbability. By the light of these new facts it has become quite a probable explanation of the whole affair, and if it could only be shown that Mr. Hornby's memorandum block was among the papers on the table, it would rise to a high degree of probability. The obvious moral is, never disregard the improbable. By the way, it is odd that Reuben failed to recall this occurrence when I questioned him. Of course, the b.l.o.o.d.y finger-marks were not discovered until he had gone, but one would have expected him to recall the circ.u.mstance when I asked him, pointedly, if he had never left b.l.o.o.d.y finger-prints on any papers."

"I must try to find out if Mr. Hornby's memorandum block was on the table and among the marked papers," I said.

"Yes, that would be wise," he answered, "though I don't suppose the information will be forthcoming."

My colleague's manner rather disappointed me. He had heard my report with the greatest attention, he had discussed it with animation, but yet he seemed to attach to the new and-as they appeared to me-highly important facts an interest that was academic rather than practical. Of course, his calmness might be a.s.sumed; but this did not seem likely, for John Thornd.y.k.e was far too sincere and dignified a character to cultivate in private life the artifices of the actor. To strangers, indeed, he presented habitually a calm and impa.s.sive exterior; but this was natural to him, and was but the outward sign of his even and judicial habit of mind.

No; there was no doubt that my startling news had left him unmoved, and this must be for one of two reasons: either he already knew all that I had told him (which was perfectly possible), or he had some other and better means of explaining the crime. I was turning over these two alternatives, not un.o.bserved by my watchful colleague, when Polton entered the room; a broad grin was on his face, and a drawing-board, that he carried like a tray, bore twenty-four neatly turned boxwood pieces.

Thornd.y.k.e at once entered into the unspoken jest that beamed from the countenance of his subordinate.

"Here is Polton with a problem for you, Jervis," he said. "He a.s.sumes that I have invented a new parlour game, and has been trying to work out the moves. Have you succeeded yet, Polton?"

"No, sir, I haven't; but I suspect that one of the players will be a man in a wig and gown."

"Perhaps you are right," said Thornd.y.k.e; "but that doesn't take you very far. Let us hear what Dr. Jervis has to say."

"I can make nothing of them," I answered. "Polton showed me the drawing this morning, and then was terrified lest he had committed a breach of confidence, and I have been trying ever since, without a glimmer of success, to guess what they can be for."

"H'm," grunted Thornd.y.k.e, as he sauntered up and down the room, teacup in hand, "to guess, eh? I like not that word 'guess' in the mouth of a man of science. What do you mean by a 'guess'?"

His manner was wholly facetious, but I professed to take his question seriously, and replied-

"By a guess, I mean a conclusion arrived at without data."

"Impossible!" he exclaimed, with mock sternness. "n.o.body but an utter fool arrives at a conclusion without data."

"Then I must revise my definition instantly," I rejoined. "Let us say that a guess is a conclusion drawn from insufficient facts."

"That is better," said he; "but perhaps it would be better still to say that a guess is a particular and definite conclusion deduced from facts which properly yield only a general and indefinite one. Let us take an instance," he continued. "Looking out of the window, I see a man walking round Paper Buildings. Now suppose I say, after the fashion of the inspired detective of the romances, 'That man is a stationmaster or inspector,' that would be a guess. The observed facts do not yield the conclusion, though they do warrant a conclusion less definite and more general."

"You'd have been right though, sir!" exclaimed Polton, who had stepped forward with me to examine the unconscious subject of the demonstration. "That gent used to be the stationmaster at Camberwell. I remember him well."

The little man was evidently greatly impressed.

"I happen to be right, you see," said Thornd.y.k.e; "but I might as easily have been wrong."

"You weren't though, sir," said Polton. "You spotted him at a glance."

In his admiration of the result he cared not a fig for the correctness of the means by which it had been attained.

"Now why do I suggest that he is a stationmaster?" pursued Thornd.y.k.e, disregarding his a.s.sistant's comment.

"I suppose you were looking at his feet," I answered. "I seem to have noticed that peculiar, splay-footed gait in stationmasters, now that you mention it."

"Quite so. The arch of the foot has given way; the plantar ligaments have become stretched and the deep calf muscles weakened. Then, since bending of the weakened arch causes discomfort, the feet have become turned outwards, by which the bending of the foot is reduced to a minimum; and as the left foot is the more flattened, so it is turned out more than the right. Then the turning out of the toes causes the legs to splay outward from the knees downwards-a very conspicuous condition in a tall man like this one-and you notice that the left leg splays out more than the other.

"But we know that depression of the arch of the foot is brought about by standing for long periods. Continuous pressure on a living structure weakens it, while intermittent pressure strengthens it; so the man who stands on his feet continuously develops a flat instep and a weak calf, while the professional dancer or runner acquires a high instep and a strong calf. Now there are many occupations which involve prolonged standing and so induce the condition of flat foot: waiters, hall-porters, hawkers, policemen, shop-walkers, salesmen, and station officials are examples. But the waiter's gait is characteristic-a quick, shuffling walk which enables him to carry liquids without spilling them. This man walks with a long, swinging stride; he is obviously not a waiter. His dress and appearance in general exclude the idea of a hawker or even a hall-porter; he is a man of poor physique and so cannot be a policeman. The shop-walker or salesman is accustomed to move in relatively confined s.p.a.ces, and so acquires a short, brisk step, and his dress tends to rather exuberant smartness; the station official patrols long platforms, often at a rapid pace, and so tends to take long strides, while his dress is dignified and neat rather than florid. The last-mentioned characteristics, you see, appear in the subject of our a.n.a.lysis; he agrees with the general description of a stationmaster. But if we therefore conclude that he is a stationmaster, we fall into the time-honoured fallacy of the undistributed middle term-the fallacy that haunts all brilliant guessers, including the detective, not only of romance, but too often also of real life. All that the observed facts justify us in inferring is that this man is engaged in some mode of life that necessitates a good deal of standing; the rest is mere guess-work."

"It's wonderful," said Polton, gazing at the now distant figure; "perfectly wonderful. I should never have known he was a stationmaster." With this and a glance of deep admiration at his employer, he took his departure.

"You will also observe," said Thornd.y.k.e, with a smile, "that a fortunate guess often brings more credit than a piece of sound reasoning with a less striking result."

"Yes, that is unfortunately the case, and it is certainly true in the present instance. Your reputation, as far as Polton is concerned, is now firmly established even if it was not before. In his eyes you are a wizard from whom nothing is hidden. But to return to these little pieces, as I must call them, for the lack of a better name. I can form no hypothesis as to their use. I seem to have no 'departure,' as the nautical phrase goes, from which to start an inquiry. I haven't even the material for guess-work. Ought I to be able to arrive at any opinion on the subject?"

Thornd.y.k.e picked up one of the pieces, fingering it delicately and inspecting with a critical eye the flat base on which it stood, and reflected for a few moments.

"It is easy to trace a connection when one knows all the facts," he said at length, "but it seems to me that you have the materials from which to form a conjecture. Perhaps I am wrong, but I think, when you have had more experience, you will find yourself able to work out a problem of this kind. What is required is constructive imagination and a rigorous exactness in reasoning. Now, you are a good reasoner, and you have recently shown me that you have the necessary imagination; you merely lack experience in the use of your faculties. When you learn my purpose in having these things made-as you will before long-you will probably be surprised that their use did not occur to you. And now let us go forth and take a brisk walk to refresh ourselves (or perhaps I should say myself) after the day's labour.

CHAPTER XI

THE AMBUSH

"I am going to ask for your collaboration in another case," said Thornd.y.k.e, a day or two later. "It appears to be one of suicide, but the solicitors to the 'Griffin' office have asked me to go down to the place, which is in the neighbourhood of Barnet, and be present at the post-mortem and the inquest. They have managed to arrange that the inquest shall take place directly after the post-mortem, so that we shall be able to do the whole business in a single visit."

"Is the case one of any intricacy?" I asked.

"I don't think so," he answered. "It looks like a common suicide; but you can never tell. The importance of the case at present arises entirely from the heavy insurance; a verdict of suicide will mean a gain of ten thousand pounds to the 'Griffin,' so, naturally, the directors are anxious to get the case settled and not inclined to boggle over a little expense."

"Naturally. And when will the expedition take place?" I asked.

"The inquest is fixed for to-morrow-what is the matter? Does that fall foul of any arrangement of yours?"

"Oh, nothing of any importance," I replied hastily, deeply ashamed of the momentary change of countenance that my friend had been so quick to observe.

"Well, what is it?" persisted Thornd.y.k.e. "You have got something on."

"It is nothing, I tell you, but what can be quite easily arranged to suit your plans."

"Cherchez la-h'm?" queried Thornd.y.k.e, with an exasperating grin.

"Yes," I answered, turning as red as a pickled cabbage; "since you are so beastly inquisitive. Miss Gibson wrote, on behalf of Mrs. Hornby, asking me to dine with them en famille to-morrow evening, and I sent off an acceptance an hour ago."

"And you call that 'nothing of any importance'!" exclaimed Thornd.y.k.e. "Alas! and likewise alackaday (which is an approximately synonymous expression)! The age of chivalry is past, indeed. Of course you must keep your appointment; I can manage quite well alone."

"We shouldn't be back early enough for me to go to Kensington from the station, I suppose?"