at about five o'clock that afternoon inspector bristol, who had spent several hours in soho upon the scene of the murder of the greek, was walking along fleet street, bound for the offices of the report. as he passed the court, on the corner of which stands a branch of the london county and provincial bank, his eye was attracted by a curious phenomenon.

there are reflectors above the bank windows which face the court, and it appeared to bristol that there was a hole in one of these, the furthermost from the corner. a tiny beam of light shone from the bank window on to the reflector, or from the reflector on to the window, which circumstance in itself was not curious. but above the reflector, at an acute angle, this mysterious beam was seemingly projected upward. walking a little way up the court he saw that it shone through, and cast a disc of light upon the ceiling of an office on the first floor of bank chambers above.

it is every detective's business to be observant, and although many thousands of passersby must have cast their eyes in the same direction that day, there is small matter for wonder in the fact that bristol alone took the trouble to inquire into the mystery—for his trained eye told him that there was a mystery here.

possibly he was in that passive frame of mind when the brain is particularly receptive of trivial impressions; for after a futile search of the soho cigar store for anything resembling a clue, he was quite resigned to the idea of failure in the case of hassan and company. he walked down the court and into the entrance of bank chambers. an inspection of the board upon the wall showed him that the first floor apparently was occupied by three firms, two of them legal, for this is the neighbourhood of the law courts, and the third a press agency. he stepped up to the first floor. past the doors bearing the names of the solicitors and past that belonging to the press agent he proceeded to a fourth suite of offices. here, pinned upon the door frame, appeared a card which bore the legend—

the congo fibre company

evidently the congo fibre company had so recently taken possession of the offices that there had been no time to inscribe their title either upon the doors or upon the board in the hall.

inspector bristol was much impressed, for into one of the rooms occupied by the fibre company shone that curious disc of light which first had drawn his attention to bank chambers. he rapped on the door, turned the handle, and entered. the sole furniture of the office in which he found himself apparently consisted of one desk and an office stool, which stool was occupied by an office boy. the windows opened on the court, and a door marked "private" evidently communicated with an inner office whose windows likewise must open on the court. it was the ceiling of this inner office, unless the detective's calculation erred, which he was anxious to inspect.

"yes, sir?" said the boy tentatively.

bristol produced a card which bore the uncompromising legend: john henry smith.

"take my card to mr. boulter, boy," he said tersely. the boy stared.

"mr. boulter, sir? there isn't any one of that name here."

"oh!" said bristol, looking around him in apparent surprise: "how long is he gone?"

"i don't know, sir. i've only been here three weeks, and mr. knowlson only took the offices a month ago."

"oh," commented bristol, "then take my card to mr. knowlson; he will probably be able to give me mr. boulter's present address."

the boy hesitated. the detective had that authoritative manner which awes the youthful mind.

"he's out, sir," he said, but without conviction.

"is he?" rapped bristol. "well, i'll leave my card."

he turned and quitted the office, carefully closing the door behind him. three seconds later he reopened it, and peering in, was in time to see the boy knock upon the private door. a little wicket, or movable panel, was let down, the card of john henry smith was passed through to someone unseen, and the wicket was reclosed!

the boy turned and met the wrathful eye of the detective. bristol reentered, closing the door behind him.

"see here, young fellow," said he, "i don't stand for those tricks! why didn't you tell me mr. knowlson was in?"

"i'm very sorry, sir!"—the boy quailed beneath his glance—"but he won't see any one who hasn't an appointment."

"is there someone with him, then?"

"no."

"well, what's he doing?"

"i don't know, sir; i've never been in to see!"

"what! never been in that room?"

"never!" declared the boy solemnly. "and i don't mind telling you," he added, recovering something of his natural confidence, "that i am leaving on the 31st. this job ain't any use to me!"

"too much work?" suggested bristol.

"no work at all!" returned the boy indignantly. "i'm just here for a blessed buffer, that's what i'm here for, a buffer!"

"what do you mean?"

"i just have to sit here and see that nobody gets into that office. lively, ain't it? where's the prospects?"

bristol surveyed him thoughtfully.

"look here, my lad," he said quietly; "is that door locked?"

"always," replied the boy.

"does mr. knowlson come to that shutter when you knock?"

"yes."

"then go and knock!"

the boy obeyed with alacrity. he rapped loudly on the door, not noticing or not caring that the visitor was standing directly behind him. the shutter was lowered and a grizzled, bearded face showed for a moment through the opening.

bristol leant over the boy and pushed a card through into the hand of the man beyond. on this occasion it did not bear the legend "john henry smith," but the following—

chief inspector bristol

c.i.d.

new scotland yard

"good afternoon, mr. knowlson," said the detective dryly. "i want to come in!"

there followed a moment of silence, from which bristol divined that he had blundered upon some mystery, possibly upon a big case; then a key was turned in the lock and the door thrown open.

"come right in, inspector," invited a strident voice. "carter, you can go home."

bristol entered warily, but not warily enough. for as the door was banged upon his entrance he faced around only in time to find himself looking down the barrel of a colt automatic.

with his back to the door which contained the wicket, now reclosed, stood the man with the bearded face. the revolver was held in his left hand; his right arm terminated in a bandaged stump. but without that his steel-gray eyes would have betrayed him to the detective.

"good god!" whispered bristol. "it's earl dexter!"

"it is!" replied the cracksman, "and you've looked in at a real inconvenient time! my visitors mostly seem to have that knack. i'll have to ask you to stay, inspector. sit down in that chair yonder."

bristol knew his man too well to think of opening any argument at that time. he sat down as directed, and ignoring the revolver which covered him all the time, began coolly to survey the room in which he found himself. in several respects it was an extraordinary apartment.

the only bright patch in the room was the shining disc upon the ceiling; and the detective noted with interest that this marked the position of an arrangement of mirrors. a white-covered table, entirely bare, stood upon the floor immediately beneath this mysterious apparatus. with the exception of one or two ordinary items of furniture and a small hand lathe, the office otherwise was unfurnished. bristol turned his eyes again upon the daring man who so audaciously had trapped him—the man who had stolen the slipper of the prophet and suffered the loss of his hand by the scimitar of an hashishin as a result. when he had least expected to find one, fate had thrown a clue in bristol's way. he reflected grimly that it was like to prove of little use to him.

"now," said dexter, "you can do as you please, of course, but you know me pretty well and i advise you to sit quiet."

"i am sitting quiet!" was the reply.

"i am sorry," continued dexter, with a quick glance at his maimed arm, "that i can't tie you up, but i am expecting a friend any moment now."

he suddenly raised the wicket with a twitch of his elbow and, without removing his gaze from the watchful detective, cried sharply—

"carter!"

but there was no reply.

"good; he's gone!"

dexter sat down facing bristol.

"i have lost my hand in this game, mr. bristol," he said genially, "and had some narrow squeaks of losing my head; but having gone so far and lost so much i'm going through, if i don't meet a funeral! you see i'm up against two tough propositions."

bristol nodded sympathetically.

"the first," continued dexter, "is you and cavanagh, and english law generally. my idea—if i can get hold of the slipper again—oh! you needn't stare; i'm out for it!—is to get the antiquarian institution to ransom it. it's a line of commercial speculation i have worked successfully before. there's a dozen rich highbrows, cranks to a man, connected with it, and they are my likeliest buyers—sure. but to keep the tone of the market healthy there's hassan of aleppo, rot him! he's a dangerous customer to approach, but you'll note i've been in negotiation with him already and am still, if not booming, not much below par!"

"quite so," said bristol. "but you've cut off a pretty hefty chew nevertheless. they used to call you the stetson man, you used to dress like a fashion plate and stop at the big hotels. those days are past, dexter, i'm sorry to note. you're down to the skulking game now and you're nearer an advert for clarkson than stein-bloch!"

"yep," said dexter sadly, "i plead guilty, but i think here's carneta!"

bristol heard the door of the outer office open, and a moment later that upon which his gaze was set opened in turn, to admit a girl who was heavily veiled, and who started and stood still in the doorway, on perceiving the situation. never for one unguarded moment did the american glance aside from his prisoner.

"the inspector's dropped in, carneta!" he drawled in his strident way. "you're handy with a ball of twine; see if you can induce him to stay the night!"

the girl, immediately recovering her composure, took off her hat in a businesslike way and began to look around her, evidently in search of a suitable length of rope with which to fasten up bristol.

"might i suggest," said the detective, "that if you are shortly quitting these offices a couple of the window-cords neatly joined would serve admirably?"

"thanks," drawled dexter, nodding to his companion, who went into the outer office, where she might be heard lowering the windows. she was gone but a few moments ere she returned again, carrying a length of knotted rope. under cover of dexter's revolver, bristol stoically submitted to having his wrists tied behind him. the end of the line was then thrown through the ventilator above the door which communicated with the outer office and bristol was triced up in such a way that, his wrists being raised behind him to an uncomfortable degree, he was almost forced to stand upon tiptoe. the line was then secured.

"very workmanlike!" commented the victim. "you'll find a large handkerchief in my inside breast pocket. it's a clean one, and i can recommend it as a gag!"

very promptly it was employed for the purpose, and inspector bristol found himself helpless and constrained in a very painful position. dexter laid down his revolver.

"we will now give you a free show, inspector," he said, genially, "of our camera obscura!"

he pulled down the blinds, which bristol noted with interest to be black, but through an opening in one of them a mysterious ray of light—the same that he had noticed from fleet street—shone upon that point in the ceiling where the arrangement of mirrors was attached. dexter made some alteration, apparently in the focus of the lens (for bristol had divined that in some way a lens had been fixed in the reflector above the bank window below) and the disc of light became concentrated. the white-covered table was moved slightly, and in the darkness some further manipulation was performed.

"observe," came the strident voice—"we now have upon the screen here a minute moving picture. this little device, which is not protected in any way, is of my own invention, and proved extremely useful in the arkwright jewel case, which startled chicago. it has proved useful now. i know almost as much concerning the arrangements below as the manager himself. in confidence, inspector, this is my last bid for the slipper! i have plunged on it. madame sforza, the distinguished italian lady who recently opened an account below, opened it for 500 pounds cash. she has drawn a portion, but a balance remains which i am resigned to lose. her motor-car (hired), her references (forged), the case of jewels which she deposited this morning (duds!)—all represent a considerable outlay. it's a nerve-racking line of operation, too. any hour of the day may bring such a visitor as yourself, for example. in short, i am at the end of my tether."

bristol, ignoring the increasing pain in his arms and wrists, turned his eyes upon the white-covered table and there saw a minute and clear-cut picture, such as one sees in a focussing screen, of the interior of the manager's office of the london county and provincial bank!