ruby reagan, expert cracksman, was busily, albeit quietly, engaged in the practice of his profession. his rubber soles fell silently upon the deep carpet as he stepped into the utter gloom of the study and closed the door noiselessly behind him. for a long time he stood perfectly still, listening, feeling with that vague single sense for the presence of some one else; then he flashed his electric light. a flat topped library table was directly in front of him, littered over with books, and to his left were the bulky outlines of a roll top desk. there were some chairs, a cabinet or so, and rows of bookcases.

his scrutiny, brief but comprehensive, seemed to satisfy reagan; for the light went out suddenly, and, turning in his tracks, he slid the bolt of the door into its socket slowly, to avoid even a click. next he released the grips on one of the windows, for it might be necessary to leave the room that way in the event of some one entering by the single door. then he settled down to work. first was the desk, and after a long, minute inspection of the lock he dropped on his knees before it and began trying his skeleton keys. the electric flash, with the light fixed, was on the left leaf of the desk, brightly illuminating the lock and lending a deeper glow of ruby red to his hair. on the right leaf of the desk, within instant reach, was his revolver.

it was nearly half an hour before the lock yielded, and then, with a sigh of relief, reagan carefully pushed up the roll top. inside he found a metal box. from a score of pigeonholes he dragged forth papers of all descriptions, ruthlessly scattering them about him after a quick examination of each in turn. then he went through drawer after drawer, carefully scrutinizing each article before he laid it down.

“guess it’s in the box,” he mused at length.

sitting flat upon the floor, with the box between his knees, he lavished his talents upon it. after a few minutes the lock clicked, and the metal lid lifted. again reagan smiled, for here were packages and packages of banknotes. but after a moment they too were spilled out on the floor. it was something else he sought.

“now, that’s funny,” he told himself finally. “it isn’t here.” he paused thoughtfully, while his eyes rested lovingly upon the packages of money. “of course, if i can’t get what i want i’ll take what i can get,” he went on at last. and he proceeded to stuff the money away in his pockets.

several times he ran his fingers slowly through his red hair. it was plain that he was deeply puzzled. he was on the point of rising to continue his investigations in other directions, when he heard something. it was a voice — a quiet, soothing, pleasant voice — about fourteen inches behind his right ear.

“don’t try to get your revolver, please!” the voice advised. “if you do, i’ll shoot!”

involuntarily reagan’s hand darted out toward the weapon on the leaf of the desk; but it was drawn back as suddenly when he heard a sharp click behind him. nonplussed for the moment, he sat down again on the floor, half expecting a shot. it didn’t come, and he screwed his head around to see why.

what he saw astounded him. it was a diaphanous, floating, lacy, white something — the figure of a girl. or was it a girl? the head was sheathed in white, the features covered by a misty, hazy, veily thing, and in the dim reflected light the whole figure seemed ridiculously unsubstantial. it was a girl’s voice, though.

“sit perfectly still, please, and don’t make any noise!” the voice advised again. yes, it was a girl’s voice.

reagan noted the small, gold mounted revolver in her right hand, with the barrel, at just that moment, on a direct line with his head and only a foot or so away; and he noted that it remained steadily where it was without one tremor or quiver.

“yes’m,” he said at last.

the white figure walked around him — or did it float? — and picked up his revolver from the desk.

“this is mr. reagan, isn’t it?” she inquired.

“yes’m,” responded reagan. the admission was surprised out of him.

“did you find it?”

“no’m.”

was this thing real? reagan rubbed his eyes doubtfully. he was dreaming, of course. he would wake up in a minute. he opened his eyes again. yes, there she was. but she wasn’t real — she couldn’t be real — she was a ghost. she was certainly not in the room when he entered, and she could not have come in since, because he had bolted the door on the inside.

“i shall trouble you now, mr. reagan,” the ghost woman went on, “to take all that money from your pocket and put it back in the box.”

reagan stared at the end of the revolver a moment, and the ghost woman wriggled it. that was real enough, anyway. promptly and without a word he began to disgorge packages of banknotes. then at last looked up again.

“you put back only eight packages,” said the ghost woman calmly. “you took out nine.”

“yes’m,” said reagan.

he fished through his pockets again, in a semi-hypnotic condition, produced more money, and deposited it with the other. he closed the metal lid and snapped the lock.

“that will do very nicely,” she said approvingly. “now i shall trouble you, please, to go on about your business.”

reagan started to rise, awkwardly enough, on hands and knees. the ghost woman stepped back a little; but still she was not far enough away, for when reagan suddenly came to his feet his outstretched arms struck her violently beneath the wrists and sent the two revolvers flying upward. with another quick movement he swept the electric light from the desk, extinguishing it. there was a sound of scuffling feet in the darkness, as of persons struggling, a little despairing cry, then finally a pistol shot.

reagan stumbled blindly about the room, seeking the door. he found it at last, still bolted on the inside, and tugged at it frantically. then came the sound of heavy feet running along the hall outside toward the study, and reagan stopped. the window! it was the only way now! the shot had aroused the household. he rushed toward the window; but it refused to move.

the clamor was at the door. desperately reagan sought for the side grips on the window; but they seemed to have disappeared. the door trembled as some heavy body was hurled against it. the bolt would yield — it was yielding — reagan heard the woodwork crack. then deliberately he drove his clenched fist through the glass, took one step on a chair and hurled himself straight through. the door crashed under the onslaught and swung inward.

on the following morning chester mills, a wealthy merchant, called on detective mallory, chief of the bureau of criminal investigation.

“i own a large country estate forty miles out of town,” mills began abruptly. “yesterday was the last day of the month. i went to the bank and drew nine hundred dollars, and placed it in a metal box in my desk at home and locked both the box and desk.

“i went to bed at eleven o’clock. about two o’clock this morning i heard a pistol shot in the study. i jumped out of bed and rushed into the hall toward the study, meeting on the way one of my servants, o’brien. we found the study locked, and started to smash the door in. as we did so we heard a great crash of glass inside.

“then we did smash the door, and o’brien turned on the electric lights. one of the two windows was smashed out as if somebody had jumped or been thrown through it; my desk had been ransacked, and my papers scattered all over the floor. the desk was standing open, and i picked up the box. it had a bullet hole in it. the ball went in the top and came out the side. i found it sticking in the desk. it was thirty-two caliber. here it is.”

mills tossed the misshapen leaden missile on the table, and detective mallory examined it.

“then i found the first real puzzle,” mills went on. “i opened the box and counted the money. instead of any of it being missing, there was more there than there was when i put the box in the desk. where there had been only nine hundred dollars, verified by the paying teller and myself, there was now nine hundred and ten dollars — an extra ten-dollar bill.”

detective mallory chewed his cigar frantically.

“o’brien found a soft black hat in the room, near the door,” continued mills, “a revolver, thirty-eight caliber, with every chamber loaded, an overcoat, an electric flashlight which had been thrown to the floor and broken, and a very complete kit of burglar’s tools. i straightened the women folk all out, had the house searched, and went back to bed. so far as i have been able to find out, nothing was stolen — nothing is missing.”

“well, in that case —” began the detective.

“i haven’t started yet,” interrupted mills tersely. “the window was out, as i said; so when we went to bed again we left o’brien in the study on watch. about halfpast three o’clock i was awakened again by a scream — a woman. again i jumped out and ran along toward the study. the lights were going, but there was no sign of o’brien. i presumed then that his attention had been attracted by the scream and he had gone to investigate. but — well, o’brien has disappeared. no one has seen or heard of him since — there’s not a trace.”

detective mallory sat for a long time silently smoking, and staring into the eyes of his caller.

at this point the problem came under the observation of that eminent logician, professor augustus s. f. x. van dusen — the thinking machine. as hutchinson hatch, reporter, related the known facts, the distinguished man of science permitted his eyes to narrow down to mere slits of watery blue, and the tall, domelike forehead was deeply furrowed.

“why was any shot fired?” hatch demanded of the scientist in perplexity. “and who fired it? were there two burglars? did they fight? was one wounded? there were bloodstains on the ground outside the window; but we can see that whoever jumped out might have cut himself on the glass. and why was the hole shot in the tin box? not to break the lock, obviously; for it could have been taken along. where does the odd ten-dollar bill in the box figure? where is o’brien? who was the woman who screamed that second time? why did she scream? why wasn’t something stolen?”

having relieved himself of this torrent of questions, hatch dropped back into his chair expectantly and lighted a cigarette. the thinking machine permitted two disapproving eyes to settle on the young man for a moment.

“and still you haven’t asked the one vital question,” he remarked tartly. “that is, what particular object in that study, or supposed to be in that study, is of such great importance to some one unknown that two bold, daring i might say, attempts were made to get it in the same night?”

“it seems to me it would be impossible to learn that, until —”

“nothing is impossible, mr. hatch. it is merely a little sum in arithmetic. two and two make four; not sometimes but all the time. this problem, at the moment, seems remarkably disjointed, particularly when we consider the disappearance of o’brien. first, then, is mr. mills positive nothing was stolen?”

“absolutely so,” replied hatch. “he has checked off every paper, and accounted for every article.”

the furrows in the tall brow deepened perceptibly, and for a long time the crabbed little scientist sat silent. “how much blood was found outside?” he asked suddenly.

“quite a good deal of it,” hatch responded. “it looks as if some one, whoever jumped or was thrown out, received some nasty cuts. the edges of the glass are stained.”

the thinking machine nodded. “it is established beyond all question that the woman who screamed that second time was not one of those in the house?” he asked.

“oh, yes,” returned hatch confidently. “they had all retired after the first fright, and the second didn’t even arouse them. they didn’t know of o’brien’s disappearance until morning.”

“the police have found nothing yet?”

“not yet. the articles left in the room, of course — the hat and coat and burglar’s tools — are clues that they are working on. they might establish identity by their aid.”

“well, we’ll have to find the man who jumped,” remarked the scientist placidly. “when we do that, we can go somewhere with this affair.”

“yes, when we do that,” hatch agreed, with a grin.

“of course we can do it!” snapped the thinking machine. “here we seek a man with neither hat nor overcoat, who is cut up with glass, possibly badly wounded.”

“but he’s the sort of man who would scuttle to cover like a scared rabbit,” hatch protested.

“wouldn’t matter how badly hurt he was, if he could walk he would hide.”

“you seem to think, mr. hatch, that leaping through a window, taking all the glass with you, and falling twenty feet to a hard pavement, is a trivial affair,” declared the scientist crabbedly. “if this man wasn’t badly hurt, it’s a miracle; therefore —” he stopped abruptly and squinted at the newspaper man. “i’m going to state a case and ask you a question,” he went on suddenly. “before i do it i’ll write the answer you will give on this bit of paper. you are an intelligent man; so i’ll demonstrate to you how intelligent minds run in the same channel.”

he scribbled a few words hurriedly, folded the paper twice, and handed it to the reporter.

“now you are the burglar,” he resumed, “a man perhaps well known to the police. you jumped from that window and hurt yourself seriously. you need medical attention; yet you can’t afford to run the slightest risk of capture. you have no hat or coat. you go to physician, not too near the scene of the affair, and you tell a story to account for your condition. what could you say to do away with all suspicion, and make yourself perfectly safe, at least for the moment?”

hatch smiled whimsically as he turned and twisted the scrap of paper in his fingers, then lighted a cigarette and got down to the matter in hand seriously.

“i think,” he said at last slowly, and feeling unaccountably sheepish about it, “that the safest story to tell the physician would be that i had been thrown from an automobile, lost my hat, say, cut myself going head foremost through the glass front when the car ran away, badly bruised by the violence with which i hit the ground; and all that sort of thing.”

the thinking machine glared at him aggressively for an instant, then arose and left the room. hatch drew a long breath, then opened the folded paper reluctantly. he found only these words:

“runaway automobile — cut by diving through glass front — hat lost — bruises and other lacerations by fall to ground.”

when the scientist returned, he wore his hat and overcoat.

“mr. hatch, go at once to mr. mills, and inquire if he has yet learned of anything being missing from the study — a paper of some sort, in all probability,” he instructed. “then, without mentioning the matter to him, take other steps to learn the nature of any litigation which might be pending in which he is concerned — i imagine something is either now going on or will be going on in a few days. run by this evening to see me.”

“are you going with me?” inquired the reporter.

“no, no,” responded the scientist impatiently. “i’m going to see the man who jumped out of the window.”

when ruby reagan, expert cracksman, awoke to consciousness he found himself gazing straight into two squinting blue eyes, magnified beyond all proportion by the thick spectacles through which he saw them. the eyes were set far back in a thin, drawn face, and above them was a shock of straw yellow hair.

“be perfectly quiet,” said the thinking machine. “you are safe enough, and in a day or so you will be all right.”

“who are you?” demanded reagan suspiciously.

“i am acting for the gentleman who employed you to get that — that document from mr. mills’s study,” replied the scientist glibly. “you are in my home. the doctor fixed you up, and i brought you here as soon as i found you. he doesn’t suspect anything. he thinks you were injured in an automobile accident, as you said.”

the cracksman closed his eyes to think about it. weakly, for he had lost much blood, he gradually pieced together a shattered recollection of events of the last few hours — the jump, his hurts, that staggering run through deserted streets to get away from that place, the final collapse at the very door of a physician, the muttered story he told to account for his wounds. then he looked again into the inscrutable face of the thinking machine. it all seemed regular enough.

“the cops don’t know?” he demanded suddenly.

“no,” replied the thinking machine emphatically. “who fired the shot?”

“the ghost lady,” replied the cracksman promptly. “guess she didn’t mean to, though, cause she seemed as anxious to be quiet as i was.”

“and of course you jumped when you heard some one at the door?”

“betcher neck!” replied reagan grimly. “the cops ain’t never had me yet, an’ i don’t intend to break no record.”

“and the ghost lady,” resumed the scientist. “tell me about her.”

and then the story of the strange happenings in the study that night as reagan recalled them was told. “and i didn’t get the paper at that,” he concluded.

“you say the ghost lady was all in white?”

“sure,” was the reply. “i don’t know really whether she was a ghost or not; but she started the mix-up.” he was silent for a moment. “but le’me tell you she must have been a ghost. she couldn’t have got in that room any other way. she slid in through the keyhole or something.”

“and she called you by name, you say?”

“yes. that’s another thing that makes me think she’s a ghost. how did she know my name. and why did she ask me if i got it?”

hutchinson hatch called an hour later. there was something of elation, excitement nearly, in his manner. he found the thinking machine stretched out in a huge chair in the laboratory, with unruffled brow, and idly twiddling fingers.

“the litigation, mr. hatch,” said the latter without turning.

“well, there are a dozen cases in which he is interested one way or another,” hatch informed him; “but there is one particularly —”

“something about property rights, i imagine?” interrupted the scientist.

“yes,” said the reporter. “there’s a fortune involved, and a vast deal of real estate. a business partner of mills, martin pendexter by name, died three or four years ago and his grandson, now about twenty-two years old, is suing to recover certain money and property from mills, alleging that mills assumed it as his own when pendexter died. mills has steadfastly refused to go into the matter, or even discuss it, and finally the boy brought the suit. it has been postponed several times; but it’s to come up for hearing soon.”

“mr. mills, then, holds title to this property?” inquired the thinking machine.

“i presume if he hadn’t felt safe in his position he would not have permitted the matter to go into court,” replied hatch. “i figure that mills does hold a release from pendexter of the property, and intends to produce it in court. he has advised the boy several times not to sue; but would never give a reason.”

“oh!” and for a long time the scientist sat silent. “of course — of course,” he mused, half aloud. “then the ghost woman was one of the —”

“and there’s another thing,” hatch rushed on impatiently. “detective downey told me a little while ago the police have established the identity of at least one person who was in the study that night, by the kit of tools left behind. his name is ruby reagan.”

“ruby reagan,” repeated the scientist thoughtfully. “oh, yes. he’s asleep in the next room there.”

the thinking machine was talking; mills, detective mallory, and hutchinson hatch were listening.

“there is no puzzle about it at all,” declared the scientist. “briefly what happened was this: a burglar was employed by a man who is suing you, mr. mills, to go into your study and find, if indeed such a thing is in existence, the document upon which you must depend to prove your title to the pendexter property now in dispute.

“well, this burglar went to that study and looked for that document — vainly, i may say here. while looking for that he found the money in the box. he was tempted then, contrary to orders, perhaps, and put this money in his pocket. later he was compelled at the point of a revolver to put the money back in the box, and in his hurry to obey orders he put in a ten-dollar bill of his own. the person who compelled him to replace the money was — was —”

he paused, wrote something on a slip of paper, and passed it to mills.

“what!” exclaimed mills incredulously.

“no names, please — yet, anyway,” broke in the scientist. “anyway, it was a woman, i may say a woman of great courage, even audacity. she had gained possession of the burglar’s revolver, and with two weapons ordered him to go. the burglar precipitated a struggle, a shot was fired by accident, perhaps, and that is the shot which went through the tin box. the burglar jumped through the window and escaped. the woman, who was in the room, perhaps behind the curtain of the door when the burglar entered, had come there to get that particular document he was seeking. at the time he jumped we can imagine how she managed to get out into the hall when the door flew open, and you and your man o’brien entered.

“the next we know of that woman she was with the others screaming. a little logic shows us that after that first fright, when the house was perfectly still again, the woman, not knowing o’brien was on watch, returned to that study again to seek that document. he was sitting in the dark, heard her, and flashed on the electric lights. she was surprised, she screamed, was recognized by o’brien, and then for some consideration that does not appear — probably a bribe — induced o’brien to disappear. again she avoided discovery, and if an investigation had been made she would have been found in bed, i dare say.

“being totally ignorant now, of the incidents leading up to the pistol shot and the burglar’s escape, the first point that the logical mind can seize upon is the finding of more money in the tin box than was known to be there. therefore, we know that that box had been opened, and we know that the burglar was either an honest man or was compelled to be honest. we know too from the fact that a thirty-eight caliber revolver was found, that there was a second revolver — the one from which the shot was fired. burglars are not honest. was this one compelled to be honest? what honest person could be in that room-lone with that burglar, remember? you see instantly a thousand possibilities.

“without pursuing those possibilities at the moment, it came down to a question of finding the burglar — the dishonest one, i may say. that was not difficult, only tedious work on the telephone, seeking a doctor who had treated a man who was probably — probably, you note — injured in an automobile accident. i found your ruby reagan, mr. mallory, and from him i learned just what happened at first — a woman in white, a ghost woman, obviously some woman in the house. white lacy gowns are not popular for street wear at two o’clock in the morning.”

“i wonder if this is absolutely necessary, mr. van dusen?” interrupted mills. his face was white. “i think i understand, and i assure you the matter has taken a personal turn which may mean a great deal to me and my family.”

the thinking machine waved his hand as if the matter was dismissed.

“for your benefit, mr. mills,” continued the scientist, “i will state that the motive for the girl’s act was one which reflected her great courage, and her loyalty to you — perhaps at the same time her regard for another man. do you follow me? in some way — perhaps the man told her — she learned of the plan to engage reagan for the work, and she could have learned of that only from the man by a relationship which partook of love for him. her loyalty to you and a natural desire to save this man’s name in your eyes, led her to seek in person to recover the document. it merely happened that they both visited the study the same night.”

the thinking machine stopped as if that was all.

“but here, go on,” detective mallory insisted. “i want to know the rest.”

“suppose, mr. mallory, that you find reagan for yourself?” suggested the thinking machine after a long pause. “i did it. surely you can.”

“where is he? where did you see him?”

“i saw him at my house,” responded the scientist calmly. “i left him there to come here; but a man who confesses what he confessed to me doesn’t stay at a place like that if he can help it. the matter is as i have stated it, mr. mills. your reason for refusing to give the young man any explanation of your holding the property is a good one, i dare say, so i’ll not question it.”

“i’ll tell you,” flamed mills suddenly. “he is not really the grandson of pendexter. i will be compelled to show that if he sues me — that is why i have advised him not to sue.”

“i imagined as much,” said the thinking machine.

ruby reagan left the home of the thinking machine in a cab late that night. and a few days later the pendexter suit was withdrawn by the plaintiff.