"i am going to ask for your collaboration in another case," said thorndyke, 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 thorndyke. "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 thorndyke, 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 thorndyke. "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?"

"no; certainly not. i find that the trains are very awkward; we should not reach king's cross until nearly one in the morning."

"then, in that case, i shall write to miss gibson and excuse myself."

"oh, i wouldn't do that," said thorndyke; "it will disappoint them, and really it is not necessary."

"i shall write forthwith," i said firmly, "so please don't try to dissuade me. i have been feeling quite uncomfortable at the thought that, all the time i have been in your employ, i seem to have done nothing but idle about and amuse myself. the opportunity of doing something tangible for my wage is too precious to be allowed to slip."

thorndyke chuckled indulgently. "you shall do as you please, my dear boy," he said; "but don't imagine that you have been eating the bread of idleness. when you see this hornby case worked out in detail, you will be surprised to find how large a part you have taken in unravelling it. your worth to me has been far beyond your poor little salary, i can assure you."

"it is very handsome of you to say that," i said, highly gratified to learn that i was really of use, and not, as i had begun to suspect, a mere object of charity.

"it is perfectly true," he answered; "and now, since you are going to help me in this case, i will set you your task. the case, as i have said, appears to be quite simple, but it never does to take the simplicity for granted. here is the letter from the solicitors giving the facts as far as they are known at present. on the shelves there you will find casper, taylor, guy and ferrier, and the other authorities on medical jurisprudence, and i will put out one or two other books that you may find useful. i want you to extract and make classified notes of everything that may bear on such a case as the present one may turn out to be. we must go prepared to meet any contingency that may arise. this is my invariable practice, and even if the case turns out to be quite simple, the labour is never wasted, for it represents so much experience gained."

"casper and taylor are pretty old, aren't they?" i objected.

"so is suicide," he retorted drily. "it is a capital mistake to neglect the old authorities. 'there were strong men before agamemnon,' and some of them were uncommonly strong, let me tell you. give your best attention to the venerable casper and the obsolete taylor and you will not be without your reward."

as a result of these injunctions, i devoted the remainder of the day to the consideration of the various methods by which a man might contrive to effect his exit from the stage of human activities. and a very engrossing study i found it, and the more interesting in view of the problem that awaited solution on the morrow; but yet not so engrossing but that i was able to find time to write a long, rather intimate and minutely explanatory letter to miss gibson, in which i even mentioned the hour of our return as showing the impossibility of my keeping my engagement. not that i had the smallest fear of her taking offence, for it is an evidence of my respect and regard for her that i cancelled the appointment without a momentary doubt that she would approve of my action; but it was pleasant to write to her at length and to feel the intimacy of keeping her informed of the details of my life.

the case, when we came to inquire into it on the spot, turned out to be a suicide of the most transparent type; whereat both thorndyke and i were, i think, a little disappointed—he at having apparently done so little for a very substantial fee, and i at having no opportunity for applying my recently augmented knowledge.

"yes," said my colleague, as we rolled ourselves up in our rugs in adjacent corners of the railway carriage, "it has been a flat affair, and the whole thing could have been managed by the local solicitor. but it is not a waste of time after all, for, you see, i have to do many a day's work for which i get not a farthing of payment, nor even any recognition, so that i do not complain if i occasionally find myself receiving more payment than my actual services merit. and as to you, i take it that you have acquired a good deal of valuable knowledge on the subject of suicide, and knowledge, as the late lord bacon remarked with more truth than originality, is power."

to this i made no reply, having just lit my pipe and feeling uncommonly drowsy; and, my companion having followed my example, we smoked in silence, becoming more and more somnolent, until the train drew up in the terminus and we turned out, yawning and shivering, on to the platform.

"bah!" exclaimed thorndyke, drawing his rug round his shoulders; "this is a cheerless hour—a quarter past one. see how chilly and miserable all these poor devils of passengers look. shall we cab it or walk?"

"i think a sharp walk would rouse our circulation after sitting huddled up in the carriage for so long," i answered.

"so do i," said thorndyke, "so let us away; hark forward! and also tally ho! in fact one might go so far as to say yoicks! that gentleman appears to favour the strenuous life, if one may judge by the size of his sprocket-wheel."

he pointed to a bicycle that was drawn up by the kerb in the approach—a machine of the road-racer type, with an enormous sprocket-wheel, indicating a gear of, at least, ninety.

"some scorcher or amateur racer, probably," i said, "who takes the opportunity of getting a spin on the wood pavement when the streets are empty." i looked round to see if i could identify the owner, but the machine appeared to be, for the moment, taking care of itself.

king's cross is one of those districts of which the inhabitants are slow in settling down for the night, and even at a quarter past one in the morning its streets are not entirely deserted. here and there the glimmer of a street lamp or the far-reaching ray from a tall electric light reveals the form of some nocturnal prowler creeping along with cat-like stealthiness, or bursting, cat-like, into unmelodious song. not greatly desirous of the society of these roysterers, we crossed quickly from the station into the gray's inn road, now silent and excessively dismal in aspect, and took our way along the western side. we had turned the curve and were crossing manchester street, when a series of yelps from ahead announced the presence of a party of merry-makers, whom we were not yet able to see, however, for the night was an exceptionally dark one; but the sounds of revelry continued to increase in volume as we proceeded, until, as we passed sidmouth street, we came in sight of the revellers. they were some half-dozen in number, all of them roughs of the hooligan type, and they were evidently in boisterous spirits, for, as they passed the entrance to the royal free hospital, they halted and battered furiously at the gate. shortly after this exploit they crossed the road on to our side, whereupon thorndyke caught my arm and slackened his pace.

"let them draw ahead," said he. "it is a wise precaution to give all hooligan gangs a very wide berth at this time of night. we had better turn down heathcote street and cross mecklenburgh square."

we continued to walk on at reduced speed until we reached heathcote street, into which we turned and so entered mecklenburgh square, where we mended our pace once more.

"the hooligan," pursued thorndyke, as we walked briskly across the silent square, "covers a multitude of sins, ranging from highway robbery with violence and paid assassination (technically known as 'bashing') down to the criminal folly of the philanthropic magistrate, who seems to think that his function in the economy of nature is to secure the survival of the unfittest. there goes a cyclist along guildford street. i wonder if that is our strenuous friend from the station. if so, he has slipped past the hooligans."

we were just entering doughty street, and, as thorndyke spoke, a man on a bicycle was visible for an instant at the crossing of the two streets. when we reached guildford street we both looked down the long, lamp-lighted vista, but the cyclist had vanished.

"we had better go straight on into theobald's road," said thorndyke, and we accordingly pursued our way up the fine old-world street, from whose tall houses our footfalls echoed, so that we seemed to be accompanied by an invisible multitude, until we reached that part where it unaccountably changes its name and becomes john street.

"there always seems to me something very pathetic about these old bloomsbury streets," said thorndyke, "with their faded grandeur and dignified seediness. they remind me of some prim and aged gentlewoman in reduced circumstances who—hallo! what was that?"

a faint, sharp thud from behind had been followed instantly by the shattering of a ground-floor window in front.

we both stopped dead and remained, for a couple of seconds, staring into the gloom, from whence the first sound had come; then thorndyke darted diagonally across the road at a swift run and i immediately followed.

at the moment when the affair happened we had gone about forty yards up john street, that is, from the place where it is crossed by henry street, and we now raced across the road to the further corner of the latter street. when we reached it, however, the little thoroughfare was empty, and, as we paused for a moment, no sound of retreating footsteps broke the silence.

"the shot certainly came from here!" said thorndyke; "come on," and he again broke into a run. a few yards up the street a mews turns off to the left, and into this my companion plunged, motioning me to go straight on, which i accordingly did, and in a few paces reached the top of the street. here a narrow thoroughfare, with a broad, smooth pavement, bears off to the left, parallel with the mews, and, as i arrived at the corner and glanced up the little street, i saw a man on a bicycle gliding swiftly and silently towards little james' street.

with a mighty shout of "stop thief!" i started in hot pursuit, but, though the man's feet were moving in an apparently leisurely manner, he drew ahead at an astonishing pace, in spite of my efforts to overtake him; and it then dawned upon me that the slow revolutions of his feet were due, in reality, to the unusually high gear of the machine that he was riding. as i realised this, and at the same moment recalled the bicycle that we had seen in the station, the fugitive swung round into little james' street and vanished.

the speed at which the man was travelling made further pursuit utterly futile, so i turned and walked back, panting and perspiring from the unwonted exertion. as i re-entered henry street, thorndyke emerged from the mews and halted on seeing me.

"cyclist?" he asked laconically, as i came up.

"yes," i answered; "riding a machine geared up to about ninety."

"ah! he must have followed us from the station," said thorndyke. "did you notice if he was carrying anything?"

"he had a walking-stick in his hand. i didn't see anything else."

"what sort of walking-stick?"

"i couldn't see very distinctly. it was a stoutish stick—i should say a malacca, probably—and it had what looked like a horn handle. i could see that as he passed a street lamp."

"what kind of lamp had he?"

"i couldn't see; but, as he turned the corner, i noticed that it seemed to burn very dimly."

"a little vaseline, or even oil, smeared on the outside of the glass will reduce the glare of a lamp very appreciably," my companion remarked, "especially on a dusty road. ha! here is the proprietor of the broken window. he wants to know, you know."

we had once more turned into john street and now perceived a man, standing on the wide doorstep of the house with the shattered window, looking anxiously up and down the street.

"do either of you gents know anything about this here?" he asked, pointing to the broken pane.

"yes," said thorndyke, "we happened to be passing when it was done; in fact," he added, "i rather suspect that the missile, whatever it was, was intended for our benefit."

"oh!" said the man. "who done it?"

"that i can't say," replied thorndyke. "whoever he was, he made off on a bicycle and we were unable to catch him."

"oh!" said the man once more, regarding us with growing suspicion. "on a bicycle, hay! dam funny, ain't it? what did he do it with?"

"that is what i should like to find out," said thorndyke. "i see this house is empty."

"yes, it's empty—leastways it's to let. i'm the caretaker. but what's that got to do with it?"

"merely this," answered thorndyke, "that the object—stone, bullet or whatever it may have been—was aimed, i believe, at me, and i should like to ascertain its nature. would you do me the favour of permitting me to look for it?"

the caretaker was evidently inclined to refuse this request, for he glanced suspiciously from my companion to me once or twice before replying, but, at length, he turned towards the open door and gruffly invited us to enter.

a paraffin lamp was on the floor in a recess of the hall, and this our conductor took up when he had closed the street door.

"this is the room," he said, turning the key and thrusting the door open; "the library they call it, but it's the front parlour in plain english." he entered and, holding the lamp above his head, stared balefully at the broken window.

thorndyke glanced quickly along the floor in the direction that the missile would have taken, and then said—

"do you see any mark on the wall there?"

as he spoke, he indicated the wall opposite the window, which obviously could not have been struck by a projectile entering with such extreme obliquity; and i was about to point out this fact when i fortunately remembered the great virtue of silence.

our friend approached the wall, still holding up the lamp, and scrutinised the surface with close attention; and while he was thus engaged, i observed thorndyke stoop quickly and pick up something, which he deposited carefully, and without remark, in his waistcoat pocket.

"i don't see no bruise anywhere," said the caretaker, sweeping his hand over the wall.

"perhaps the thing struck this wall," suggested thorndyke, pointing to the one that was actually in the line of fire. "yes, of course," he added, "it would be this one—the shot came from henry street."

the caretaker crossed the room and threw the light of his lamp on the wall thus indicated.

"ah! here we are!" he exclaimed, with gloomy satisfaction, pointing to a small dent in which the wall-paper was turned back and the plaster exposed; "looks almost like a bullet mark, but you say you didn't hear no report."

"no," said thorndyke, "there was no report; it must have been a catapult."

the caretaker set the lamp down on the floor and proceeded to grope about for the projectile, in which operation we both assisted; and i could not suppress a faint smile as i noted the earnestness with which thorndyke peered about the floor in search of the missile that was quietly reposing in his waistcoat pocket.

we were deep in our investigations when there was heard an uncompromising double knock at the street door, followed by the loud pealing of a bell in the basement.

"bobby, i suppose," growled the caretaker. "here's a blooming fuss about nothing." he caught up the lamp and went out, leaving us in the dark.

"i picked it up, you know," said thorndyke, when we were alone.

"i saw you," i answered.

"good; i applaud your discretion," he rejoined. the caretaker's supposition was correct. when he returned, he was accompanied by a burly constable, who saluted us with a cheerful smile and glanced facetiously round the empty room.

"our boys," said he, nodding towards the broken window; "they're playful lads, that they are. you were passing when it happened, sir, i hear."

"yes," answered thorndyke; and he gave the constable a brief account of the occurrence, which the latter listened to, notebook in hand.

"well," said he when the narrative was concluded, "if those hooligan boys are going to take to catapults they'll make things lively all round."

"you ought to run some of 'em in," said the caretaker.

"run 'em in!" exclaimed the constable in a tone of disgust; "yes! and then the magistrate will tell 'em to be good boys and give 'em five shillings out of the poor-box to buy illustrated testaments. i'd testament them, the worthless varmints!"

he rammed his notebook fiercely into his pocket and stalked out of the room into the street, whither we followed.

"you'll find that bullet or stone when you sweep up the room," he said, as he turned on to his beat; "and you'd better let us have it. good night, sir."

he strolled off towards henry street, while thorndyke and i resumed our journey southward.

"why were you so secret about that projectile?" i asked my friend as we walked up the street.

"partly to avoid discussion with the caretaker," he replied; "but principally because i thought it likely that a constable would pass the house and, seeing the light, come in to make inquiries."

"and then?"

"then i should have had to hand over the object to him."

"and why not? is the object a specially interesting one?"

"it is highly interesting to me at the present moment," replied thorndyke, with a chuckle, "because i have not examined it. i have a theory as to its nature, which theory i should like to test before taking the police into my confidence."

"are you going to take me into your confidence?" i asked.

"when we get home, if you are not too sleepy," he replied.

on our arrival at his chambers, thorndyke desired me to light up and clear one end of the table while he went up to the workshop to fetch some tools. i turned back the table cover, and, having adjusted the gas so as to light this part of the table, waited in some impatience for my colleague's return. in a few minutes he re-entered bearing a small vice, a metal saw and a wide-mouthed bottle.

"what have you got in that bottle?" i asked, perceiving a metal object inside it.

"that is the projectile, which i have thought fit to rinse in distilled water, for reasons that will presently appear."

he agitated the bottle gently for a minute or so, and then, with a pair of dissecting forceps, lifted out the object and held it above the surface of the water to drain, after which he laid it carefully on a piece of blotting-paper.

i stooped over the projectile and examined it with great curiosity, while thorndyke stood by regarding me with almost equal interest.

"well," he said, after watching me in silence for some time, "what do you see?"

"i see a small brass cylinder," i answered, "about two inches long and rather thicker than an ordinary lead pencil. one end is conical, and there is a small hole at the apex which seems to contain a steel point; the other end is flat, but has in the centre a small square projection such as might fit a watch-key. i notice also a small hole in the side of the cylinder close to the flat end. the thing looks like a miniature shell, and appears to be hollow."

"it is hollow," said thorndyke. "you must have observed that, when i held it up to drain, the water trickled out through the hole at the pointed end."

"yes, i noticed that."

"now take it up and shake it."

i did so and felt some heavy object rattle inside it.

"there is some loose body inside it," i said, "which fits it pretty closely, as it moves only in the long diameter."

"quite so; your description is excellent. and now, what is the nature of this projectile?"

"i should say it is a miniature shell or explosive bullet."

"wrong!" said thorndyke. "a very natural inference, but a wrong one."

"then what is the thing?" i demanded, my curiosity still further aroused.

"i will show you," he replied. "it is something much more subtle than an explosive bullet—which would really be a rather crude appliance—admirably thought out and thoroughly well executed. we have to deal with a most ingenious and capable man."

i was fain to laugh at his enthusiastic appreciation of the methods of his would-be assassin, and the humour of the situation then appeared to dawn on him, for he said, with an apologetic smile—

"i am not expressing approval, you must understand, but merely professional admiration. it is this class of criminal that creates the necessity for my services. he is my patron, so to speak; my ultimate employer. for the common crook can be dealt with quite efficiently by the common policeman!"

while he was speaking he had been fitting the little cylinder between two pads of tissue-paper in the vice, which he now screwed up tight. then, with the fine metal saw, he began to cut the projectile, lengthwise, into two slightly unequal parts. this operation took some time, especially since he was careful not to cut the loose body inside, but at length the section was completed and the interior of the cylinder exposed, when he released it from the vice and held it up before me with an expression of triumph.

"now, what do you make it?" he demanded.

i took the object in my fingers and looked at it closely, but was at first more puzzled than before. the loose body i now saw to be a cylinder of lead about half an inch long, accurately fitting the inside of the cylinder but capable of slipping freely backwards and forwards. the steel point which i had noticed in the hole at the apex of the conical end, was now seen to be the pointed termination of a slender steel rod which projected fully an inch into the cavity of the cylinder, and the conical end itself was a solid mass of lead.

"well?" queried thorndyke, seeing that i was still silent.

"you tell me it is not an explosive bullet," i replied, "otherwise i should have been confirmed in that opinion. i should have said that the percussion cap was carried by this lead plunger and struck on the end of that steel rod when the flight of the bullet was suddenly arrested."

"very good indeed," said thorndyke. "you are right so far that this is, in fact, the mechanism of a percussion shell.

"but look at this. you see this little rod was driven inside the bullet when the latter struck the wall. let us replace it in its original position."

he laid the end of a small flat file against the end of the rod and pressed it firmly, when the rod slid through the hole until it projected an inch beyond the apex of the cone. then he handed the projectile back to me.

a single glance at the point of the steel rod made the whole thing clear, and i gave a whistle of consternation; for the "rod" was a fine tube with a sharply pointed end.

"the infernal scoundrel!" i exclaimed; "it is a hypodermic needle."

"yes. a veterinary hypodermic, of extra large bore. now you see the subtlety and ingenuity of the whole thing. if he had had a reasonable chance he would certainly have succeeded."

"you speak quite regretfully," i said, laughing again at the oddity of his attitude towards the assassin.

"not at all," he replied. "i have the character of a single-handed player, but even the most self-reliant man can hardly make a post-mortem on himself. i am merely appreciating an admirable piece of mechanical design most efficiently carried out. observe the completeness of the thing, and the way in which all the necessities of the case are foreseen and met. this projectile was discharged from a powerful air-gun—the walking-stick form—provided with a force-pump and key. the barrel of that gun was rifled."

"how do you know that?" i asked.

"well, to begin with, it would be useless to fit a needle to the projectile unless the latter was made to travel with the point forwards; but there is direct evidence that the barrel was rifled. you notice the little square projection on the back surface of the cylinder. that was evidently made to fit a washer or wad—probably a thin plate of soft metal which would be driven by the pressure from behind into the grooves of the rifling and thus give a spinning motion to the bullet. when the latter left the barrel, the wad would drop off, leaving it free."

"i see. i was wondering what the square projection was for. it is, as you say, extremely ingenious."

"highly ingenious," said thorndyke, enthusiastically, "and so is the whole device. see how perfectly it would have worked but for a mere fluke and for the complication of your presence. supposing that i had been alone, so that he could have approached to a shorter distance. in that case he would not have missed, and the thing would have been done. you see how it was intended to be done, i suppose?"

"i think so," i answered; "but i should like to hear your account of the process."

"well, you see, he first finds out that i am returning by a late train—which he seems to have done—and he waits for me at the terminus. meanwhile he fills the cylinder with a solution of a powerful alkaloidal poison, which is easily done by dipping the needle into the liquid and sucking at the small hole near the back end, when the piston will be drawn up and the liquid will follow it. you notice that the upper side of the piston is covered with vaseline—introduced through the hole, no doubt—which would prevent the poison from coming out into the mouth, and make the cylinder secure from leakage. on my arrival, he follows me on his bicycle until i pass through a sufficiently secluded neighbourhood. then he approaches me, or passes me and waits round a corner, and shoots at pretty close range. it doesn't matter where he hits me; all parts are equally vital, so he can aim at the middle of my back. then the bullet comes spinning through the air point foremost; the needle passes through the clothing and enters the flesh, and, as the bullet is suddenly stopped, the heavy piston flies down by its own great momentum and squirts out a jet of the poison into the tissues. the bullet then disengages itself and drops on to the ground.

"meanwhile, our friend has mounted his bicycle and is off, and when i feel the prick of the needle, i turn, and, without stopping to look for the bullet, immediately give chase. i am, of course, not able to overtake a man on a racing machine, but still i follow him some distance. then the poison begins to take effect—the more rapidly from the violent exercise—and presently i drop insensible. later on, my body is found. there are no marks of violence, and probably the needle-puncture escapes observation at the post-mortem, in which case the verdict will be death from heart-failure. even if the poison and the puncture are discovered, there is no clue. the bullet lies some streets away, and is probably picked up by some boy or passing stranger, who cannot conjecture its use, and who would never connect it with the man who was found dead. you will admit that the whole plan has been worked out with surprising completeness and foresight."

"yes," i answered; "there is no doubt that the fellow is a most infernally clever scoundrel. may i ask if you have any idea who he is?"

"well," thorndyke replied, "seeing that, as carlyle has unkindly pointed out, clever people are not in an overwhelming majority, and that, of the clever people whom i know, only a very few are interested in my immediate demise, i am able to form a fairly probable conjecture."

"and what do you mean to do?"

"for the present i shall maintain an attitude of masterly inactivity and avoid the night air."

"but, surely," i exclaimed, "you will take some measures to protect yourself against attempts of this kind. you can hardly doubt now that your accident in the fog was really an attempted murder."

"i never did doubt it, as a matter of fact, although i prevaricated at the time. but i have not enough evidence against this man at present, and, consequently, can do nothing but show that i suspect him, which would be foolish. whereas, if i lie low, one of two things will happen; either the occasion for my removal (which is only a temporary one) will pass, or he will commit himself—will put a definite clue into my hands. then we shall find the air-cane, the bicycle, perhaps a little stock of poison, and certain other trifles that i have in my mind, which will be good confirmatory evidence, though insufficient in themselves. and now, i think, i must really adjourn this meeting, or we shall be good for nothing to-morrow."