The Treasure-Train

  V

  THE PHANTOM DESTROYER

  "Guy Fawkes himself would shudder in that mill. Think of it--fiveexplosions on five successive days, and not a clue!"

  Our visitor had presented a card bearing the name of Donald MacLeod,chief of the Nitropolis Powder Company's Secret Service. It was plainthat he was greatly worried over the case about which he had at lastbeen forced to consult Kennedy.

  As he spoke, I remembered having read in the despatches about theexplosions, but the accounts had been so meager that I had not realizedthat there was anything especially unusual about them, for it was atthe time when accidents in and attacks on the munitions-plants were ofcommon occurrence.

  "Why," went on MacLeod, "the whole business is as mysterious as ifthere were some phantom destroyer at work! The men are so frightenedthat they threaten to quit. Several have been killed. There's somethingstrange about that, too. There are ugly rumors of poisonous gases beingresponsible, quite as much as the explosions, though, so far, I've beenable to find nothing in that notion."

  "What sort of place is it?" asked Kennedy, interested at once.

  "Well, you see," explained MacLeod, "since the company's business hasincreased so fast lately, it has been forced to erect a new plant.Perhaps you have heard of the Old Grove Amusement Park, which failed?It's not far from that."

  MacLeod looked at us inquiringly, and Kennedy nodded to go on, though Iam sure neither of us was familiar with the place.

  "They've called the new plant Nitropolis--rather a neat name for apowder-works, don't you think?" resumed MacLeod. "Everything went alongall right until a few days ago. Then one of the buildings, astorehouse, was blown up. We couldn't be sure that it was an accident,so we redoubled our precautions. It was of no use. That started it. Thevery next day another building was blown up, then another, until nowthere have been five of them. What may happen to-day Heaven only knows!I want to get back as soon as I can."

  "Rather too frequent, I must admit, to be coincidences," remarkedKennedy.

  "No; they can't all be accidents," asserted MacLeod, confidently."There's too great regularity for that. I think I've considered almosteverything. I don't see how they can be from bombs placed by workmen.At least, it's not a bit likely. Besides, the explosions all occur inbroad daylight, not at night. We're very careful about the men weemploy, and they're watched all the time. The company has a guard ofits own, twenty-five picked men, under me--all honorably dischargedUnited States army men."

  "You have formed no theory of your own?" queried Kennedy.

  MacLeod paused, then drew from his pocket the clipping of a despatchfrom the front in which one of the war correspondents reported thedestruction of wire entanglements with heat supposed to have beenapplied by the use of reflecting mirrors.

  "I'm reduced to pure speculation," he remarked. "To-day they seem to bereviving all the ancient practices. Maybe some one is going at it likeArchimedes."

  "Not impossible," returned Craig, handing back the clipping. "Buffontested the probability of the achievement of Archimedes in setting fireto the ships of Marcellus with mirrors and the sun's rays. Heconstructed a composite mirror of a hundred and twenty-eight planemirrors, and with it he was able to ignite wood at two hundred and tenfeet. However, I shrewdly suspect that, even if this story is true,they are using hydrogen or acetylene flares over there. But none ofthese things would be feasible in your case. You'd know it."

  "Could it be some one who is projecting a deadly wireless force whichcauses the explosions?" I put in, mindful of a previous case ofKennedy's. "We all know that inventors have been working for years onthe idea of making explosives obsolete and guns junk. If some one hashit on a way of guiding an electric wave through the air andconcentrating power at a point, munitions-plants could be wiped out."

  MacLeod looked anxiously from me to Kennedy, but Craig betrayed nothingby his face except his interest.

  "Sometimes I have imagined I heard a peculiar, faint, whirring noise inthe air," he remarked, thoughtfully. "I thought of having the men onthe watch for air-ships, but they've never seen a trace of one. Itmight be some power either like this," he added, shaking the clipping,"or like that which Mr. Jameson suggests."

  "It's something like that you meant, I presume, when you called it a'phantom destroyer' a moment ago?" asked Kennedy.

  MacLeod nodded.

  "If you're interested," he pursued, hastily, "and feel like going downthere to look things over, I think the best place for you to go wouldbe to the Sneddens'. They're some people who have seen a chance to makea little money out of the boom. Many visitors are now coming and goingon business connected with the new works. They have started aboarding-house--or, rather, Mrs. Snedden has. There's a daughter, too,who seems to be very popular." Kennedy glanced whimsically at me.

  "Well, Walter," he remarked, tentatively, "entirely aside from theyoung lady, this ought to make a good story for the Star."

  "Indeed it ought!" I replied, enthusiastically.

  "Then you'll go down to Nitropolis?" queried MacLeod, eagerly. "You cancatch a train that will get you there about noon. And the company willpay you well."

  "MacLeod, with the mystery, Miss Snedden, and the remuneration, you areirresistible," smiled Kennedy.

  "Thank you," returned the detective. "You won't regret it. I can't tellyou how much relieved I feel to have some one else, and, above all,yourself, on the case. You can get a train in half an hour. I think itwould be best for you to go as though you had no connection with me--atleast for the present."

  Kennedy agreed, and MacLeod excused himself, promising to be on thetrain, although not to ride with us, in case we should be the target oftoo inquisitive eyes.

  For a few moments, while our taxicab was coming, Kennedy consideredthoughtfully what the company detective had said. By the time thevehicle arrived he had hurriedly packed up some apparatus in two largegrips, one of which it fell to my lot to carry.

  The trip down to Nitropolis was uninteresting, and we arrived at thelittle station shortly after noon. MacLeod was on the train, but didnot speak to us, and it was perhaps just as well, for the cabmen andothers hanging about the station were keenly watching new arrivals, andany one with MacLeod must have attracted attention. We selected orwere, rather, selected by one of the cabmen and driven immediately tothe Snedden house. Our cover was, as Craig and I had decided, to poseas two newspaper men from New York, that being the easiest way toaccount for any undue interest we might show in things.

  The powder-company's plant was situated on a large tract of land whichwas surrounded by a barbed-wire fence, six feet high and constructed ina manner very similar to the fences used in protecting prison-camps inwar-times. At various places along the several miles of fence gateswere placed, with armed guards. Many other features were suggestive ofwar-times. One that impressed us most was that each workman had tocarry a pass similar, almost, to a passport. This entire fence, welearned, was patrolled day and night by armed guards.

  A mile or so from the plant, or just outside the main gate, quite asettlement had grown up, like a mushroom, almost overnight--the productof a flood of new money. Originally, there had been only one house forsome distance about--that of the Sneddens. But now there were scores ofhouses, mostly those of officials and managers, some of them reallypretentious affairs. MacLeod himself lived in one of them, and we couldsee him ahead of us, being driven home.

  The workmen lived farther along the line, in a sort of company town,which at present greatly resembled a Western mining-camp, thoughultimately it was to be a bungalow town.

  Just at present, however, it was the Snedden house that interested usmost, for we felt the need of getting ourselves established in thisstrange community. It was an old-fashioned farm-house and had beenpurchased very cheaply by Snedden several years before. He had alteredit and brought it up to date, and the combination of old and new provedto be typical of the owner as well as of the house.

  Kennedy carried off well the critical situation of our i
ntroduction,and we found ourselves welcomed rather than scrutinized as intruders.

  Garfield Snedden was much older than his second wife, Ida. In fact, shedid not seem to be much older than Snedden's daughter Gertrude, whomMacLeod had already mentioned--a dashing young lady, never intended bynature to vegetate in the rural seclusion that her father had soughtbefore the advent of the powder-works. Mrs. Snedden was one of thosecapable women who can manage a man without his knowing it. Indeed, onefelt that Snedden, who was somewhat of both student and dreamer, neededa manager.

  "I'm glad your train was on time," bustled Mrs. Snedden. "Luncheon willbe ready in a few moments now."

  We had barely time to look about before Gertrude led us into thedining-room and introduced us to the other boarders.

  Knowing human nature, Kennedy was careful to be struck with admirationand amazement at everything we had seen in our brief whirl throughNitropolis. It was not a difficult or entirely assumed feeling, either,when one realized that, only a few short months before, the region hadbeen nothing better than an almost hopeless wilderness of scrub-pines.

  We did not have to wait long before the subject uppermost in our mindswas brought up--the explosions.

  Among the boarders there were at least two who, from the start,promised to be interesting as well as important. One was a tall,slender chap named Garretson, whose connection with the company, Igathered from the conversation, took him often on important matters toNew York. The other was an older man, Jackson, who seemed to beconnected with the management of the works, a reticent fellow, moregiven to listening to others than to talking himself.

  "Nothing has happened so far to-day, anyhow," remarked Garretson,tapping the back of his chair with his knuckle, as a token of respectfor that evil spirit who seems to be exorcised by knocking wood.

  "Oh," exclaimed Gertrude, with a little half-suppressed shudder, "I dohope those terrible explosions are at last over!"

  "If I had my way," asserted Garretson, savagely, "I'd put this townunder martial law until they WERE over."

  "It may come to that," put in Jackson, quietly.

  "Quite in keeping with the present tendency of the age," agreedSnedden, in a tone of philosophical disagreement.

  "I don't think it makes much difference how you accomplish the result,Garfield," chimed in his wife, "as long as you accomplish it, and it isone that should be accomplished."

  Snedden retreated into the refuge of silence. Though this was only abit of the conversation, we soon found out that he was an avowedpacifist. Garretson, on the other hand, was an ardent militarist, agood deal of a fire-eater. I wondered whether there might not be a gooddeal of the poseur about him, too.

  It needed no second sight to discover that both he and Gertrude weredeeply interested in each other. Garretson was what Broadway would call"a live one," and, though there is nothing essentially wrong in that, Ifancied that I detected, now and then, an almost maternal solicitude onthe part of her stepmother, who seemed to be watching both the youngman and her husband alternately. Once Jackson and Mrs. Sneddenexchanged glances. There seemed to be some understanding between them.

  The time to return to the works was approaching, and we all rose.Somehow, Gertrude and Garretson seemed naturally to gravitate towardthe door together.

  Some distance from the house there was a large barn. Part of it hadbeen turned into a garage, where Garretson kept a fast car. Jackson,also, had a roadster. In fact, in this new community, with itssuperabundant new wealth, everybody had a car.

  Kennedy and I sauntered out after the rest. As we turned an angle ofthe house we came suddenly upon Garretson in his racer, talking toGertrude. The crunch of the gravel under our feet warned them before wesaw them, but not before we could catch a glimpse of a warning fingeron the rosy lips of Gertrude. As she saw us she blushed ever soslightly.

  "You'll be late!" she cried, hastily. "Mr. Jackson has been gone fiveminutes."

  "On foot," returned Garretson, nonchalantly. "I'll overtake him inthirty seconds." Nevertheless, he did not wait longer, but swung up theroad at a pace which was the admiration of all speed-lovingNitropolitans.

  Craig had ordered our taxicab driver to stop for us after lunch, and,without exciting suspicion, managed to stow away the larger part of thecontents of our grips in his car.

  Still without openly showing our connection with MacLeod, Kennedysought out the manager of the works, and, though scores ofcorrespondents and reporters from various newspapers had vainly appliedfor permission to inspect the plant, somehow we seemed to receive thefreedom of the place and without exciting suspicion. Craig's first movewas to look the plant over. As we approached it our attention wasinstantly attracted to the numerous one-story galvanized-iron buildingsthat appeared to stretch endlessly in every direction. They seemed tobe of a temporary nature, though the power-plants, offices, and othernecessary buildings were very substantially built. The framework of thefactory-buildings was nothing but wood, covered by iron sheathing, andeven the sides seemed to be removable. The floors, however, were ofconcrete.

  "They serve their purpose well," observed Kennedy, as we picked our wayabout. "Explosions at powder-mills are frequent, anyhow. After anexplosion there is very little debris to clear away, as you mayimagine. These buildings are easily repaired or replaced, and they keepa large force of men for these purposes, as well as materials for anyemergency."

  One felt instinctively the hazard of the employment. Everywhere weresigns telling what not and what to do. One that stuck in my mind was,"It is better to be careful than sorry." Throughout the plant atfrequent intervals were first-aid stations with kits for all sorts ofaccidents, including respirators, for workmen were often overcome byether or alcohol fumes. Everything was done to minimize the hazard, yetone could not escape the conviction that human life and limb were asmuch a cost of production in this industry as fuel and raw material.

  Once, in our wanderings about the plant, I recall we ran across bothGarretson and Jackson in one of the offices. They did not see us, butseemed to be talking very earnestly about something. What it was wecould not guess, but this time it seemed to be Jackson who was doingmost of the talking. Kennedy watched them as they parted.

  "There's something peculiar under the surface with those people at theboarding-house," was all he observed. "Come; over there, about aneighth of a mile, I think I see evidences of the latest of theexplosions. Let's look at it."

  MacLeod had evidently reasoned that, sooner of later, Kennedy wouldappear in this part of the grounds, and as we passed one of the shopshe joined us.

  "You mentioned something about rumors of poisonous gases," hintedCraig, as we walked along.

  "Yes," assented MacLeod; "I don't know what there is in it. I supposeyou know that there is a very poisonous gas, carbon monoxide, orcarbonic oxide, formed in considerable quantity by the explosion ofseveral of the powders commonly used in shells. The gas has the curiouspower of combining with the blood and refusing to let go, thus keepingout the oxygen necessary for life. It may be that that is what accountsfor what we've seen--that it is actual poisoning to death of men notkilled by the immediate explosion."

  We had reached the scene of the previous day's disaster. No effort hadyet been made to clear it up. Kennedy went over it carefully. What itwas he found I do not know, but he had not spent much time before heturned to me.

  "Walter," he directed, "I wish you would go back to the office near thegate, where I left that paraphernalia we brought down. Carry itover--let me see--there's an open space there on that knoll. I'll joinyou there."

  Whatever was in the packages was both bulky and heavy, and I was gladto reach the hillside he had indicated.

  Craig was waiting for me there with MacLeod, and at once opened thepackages. From them he took a thin steel rod, which he set up in thecenter of the open space. To it he attached a frame and to the framewhat looked like four reversed megaphones. Attached to the frame, whichwas tubular, was an oak box with a little arrangement of hard rubberand metal wh
ich fitted into the ears. For some time Kennedy's face worea set, far-away expression, as if he were studying something.

  "The explosions seem always to occur in the middle of the afternoon,"observed MacLeod, fidgeting apprehensively.

  Kennedy motioned petulantly for silence. Then suddenly he pulled thetubes out of his ears and gazed about sharply.

  "There's something in the air!" he cried. "I can hear it!"

  MacLeod and I strained our eyes. There was nothing visible.

  "This is an anti-aircraft listening-post, such as the French use,"explained Craig, hurriedly. "Between the horns and the microphone inthe box you can catch the hum of an engine, even when it is muffled. Ifthere's an aeroplane or a Zeppelin about, this thing would locate it."

  Still, there was nothing that we could see, though now the sound wasjust perceptible to the ear if one strained his attention a bit. Ilistened. It was plain in the detector; yet nothing was visible. Whatstrange power could it be that we could not see or feel in broaddaylight?

  Just then came a low rumbling, and then a terrific roar from thedirection of the plant. We swung about in time to see a huge cloud ofdebris lifted literally into the air above the tree-tops and dropped toearth again. The silence that succeeded the explosion was eloquent. Thephantom destroyer had delivered his blow again.

  "The distillery--where we make the denatured alcohol!" cried MacLeod,gazing with tense face as from other buildings, we could see menpouring forth, panic-stricken, and the silence was punctured by shouts.Kennedy bent over his detector.

  "That same mysterious buzzing," he muttered, "only fainter."

  Together we hastened now toward the distillery, another of thosecorrugated-iron buildings. It had been completely demolished. Here andthere lay a dark, still mass. I shuddered. They were men!

  As we ran toward the ruin we crossed a baseball-field which the companyhad given the men. I looked back for Kennedy. He had paused at the wirebackstop behind the catcher. Something caught in the wires interestedhim. By the time I reached him he had secured it--a long, slender metaltube, cleverly weighted so as to fall straight.

  "Not a hundred per cent. of hits, evidently," he muttered. "Still, onewas enough."

  "What is it?" asked MacLeod.

  "An incendiary pastille. On contact, the nose burns away anything ithits, goes right through corrugated iron. It carries a charge ofthermit ignited by this piece of magnesium ribbon. You know whatthermit will penetrate with its thousands of degrees of heat. Only thenose of this went through the netting and never touched a thing. Thisdidn't explode anything, but another one did. Thousands of gallons ofalcohol did the rest."

  Kennedy had picked up his other package as we ran, and was now busilyunwrapping it. I looked about at the crowd that had collected, and sawthat there was nothing we could do to help. Once I caught sight ofGertrude's face. She was pale, and seemed eagerly searching for someone. Then, in the crowd, I lost her. I turned to MacLeod. He wasplainly overwhelmed. Kennedy was grimly silent and at work on somethinghe had jammed into the ground.

  "Stand back!" he cautioned, as he touched a match to the thing. With amuffled explosion, something whizzed and shrieked up into the air likea sky-rocket.

  Far above, I could now see a thing open out like a parachute, whilebelow it trailed something that might have been the stick of therocket. Eagerly Kennedy followed the parachute as the wind wafted italong and it sank slowly to the earth. When, at last, he recovered it Isaw that between the parachute and the stick was fastened a small,peculiar camera.

  "A Scheimpflug multiple camera," he explained as he seized it almostravenously. "Is there a place in town where I can get the films in thisdeveloped quickly?"

  MacLeod, himself excited now, hurried us from the scene of theexplosion to a local drug-store, which combined most of the functionsof a general store, even being able to improvise a dark-room in whichKennedy could work.

  It was some time after the excitement over the explosion had quieteddown that MacLeod and I, standing impatiently before the drug-store,saw Snedden wildly tearing down the street in his car. He saw us andpulled up at the curb with a jerk.

  "Where's Gertrude?" he shouted, wildly. "Has any one seen my daughter?"

  Breathlessly he explained that he had been out, had returned to findhis house deserted, Gertrude gone, his wife gone, even Jackson's cargone from the barn. He had been to the works. Neither Garretson norJackson had been seen since the excitement of the explosion, they toldhim. Garretson's racer was gone, too. There seemed to have been a sortof family explosion, also.

  Kennedy had heard the loud talking and had left his work to thedruggist to carry on and joined us. There was no concealment now of ourconnection with MacLeod, for it was to him that every one in town camewhen in trouble.

  In almost no time, so accurately did he keep his fingers on the feveredpulse of Nitropolis, MacLeod had found out that Gertrude had been seendriving away from the company's grounds with some one in Garretson'scar, probably Garretson himself. Jackson had been seen hurrying downthe street. Some one else had seen Ida Snedden in Jackson's car, alone.

  Meanwhile, over the wire, MacLeod had sent out descriptions of the fourpeople and the two cars, in the hope of intercepting them before theycould be plunged into the obscurity of any near-by city. Not contentwith that, MacLeod and Kennedy started out in the former's car, while Iclimbed in with Snedden, and we began a systematic search of the roadsout of Nitropolis.

  As we sped along, I could not help feeling, though I said nothing,that, somehow, the strange disappearances must have something to dowith the mysterious phantom destroyer. I did not tell even Sneddenabout the little that Kennedy had discovered, for I had learned that itwas best to let Craig himself tell, at his own time and in his own way.But the man seemed frantic in his search, and I could not help theimpression that there was something, perhaps only a suspicion, that heknew which might shed some light.

  We were coming down the river, or, rather, the bay, after a fruitlesssearch of unfrequented roads and were approaching the deserted OldGrove Amusement Park, to which excursions used, years ago, to come inboats. No one could make it pay, and it was closed and going to ruin.There had been some hint that Garretson's racer might have disappeareddown this unfrequented river road.

  As we came to a turn in the road, we could see Kennedy and MacLeod intheir car, coming up. Instead of keeping on, however, they turned intothe grove, Kennedy leaning far over the running-board as MacLeod droveslowly, following his directions, as though Craig were tracingsomething.

  With a hurried exclamation of surprise, Snedden gave our car the gasand shot ahead, swinging around after them. They were headed, followingsome kind of tire-tracks, toward an old merry-go-round that wasdismantled and all boarded up. They heard us coming and stopped.

  "Has any one told you that Garretson's car went down the river road,too?" called Snedden, anxiously.

  "No; but some one thought he saw Jackson's car come down here," calledback MacLeod.

  "Jackson's?" exclaimed Snedden.

  "Maybe both are right," I ventured, as we came closer. "What made youturn in here?'"

  "Kennedy thought he saw fresh tire-tracks running into the grove."

  We were all out of our cars by this time, and examining the softroadway with Craig. It was evident to any one that a car had been runin, and not so very long ago, in the direction of the merry-go-round.

  We followed the tracks on foot, bending about the huge circle of abuilding until we came to the side away from the road. The tracksseemed to run right in under the boards.

  Kennedy approached and touched the boards. They were loose. Some onehad evidently been there, had taken them down, and put them up. Infact, by the marks on them, it seemed as though he had made a practiceof doing so.

  MacLeod and Kennedy unhooked the boarding, while Snedden looked on in asort of daze. They had taken down only two or three sections, whichindicated that that whole side might similarly be removed, when I hearda low, startled exclamat
ion from Snedden.

  We peered in. There, in the half-light of the gloomy interior, we couldsee a car. Before we knew it Snedden had darted past us. An instantlater I distinguished what his more sensitive eye had seen--a woman,all alone in the car, motionless.

  "Ida!" he cried.

  There was no answer.

  "She--she's dead!" he shouted.

  It was only too true. There was Ida Snedden, seated in Jackson's car inthe old deserted building, all shut up--dead.

  Yet her face was as pink as if she were alive and the blood had beenwhipped into her cheeks by a walk in the cold wind.

  We looked at one another, at a loss. How did she get there--and why?She must have come there voluntarily. No one had seen any one else withher in the car.

  Snedden was now almost beside himself.

  "Misfortunes never come singly," he wailed. "My daughter Gertrudegone--now my wife dead. Confound that young fellow Garretson--andJackson, too! Where are they? Why have they fled? The scoundrels--theyhave stolen my whole family. Oh, what shall I do? what shall I do?"

  Trying to quiet Snedden, at the same time we began to look about thebuilding. On one side was a small stove, in which were still the dyingcoals of a fire. Near by were a work-bench, some tools, pieces of wire,and other material. Scattered about were pieces of material that lookedlike celluloid. Some one evidently used the place as a secret workshop.Kennedy picked up a piece of the celluloid-like stuff and carefullytouched a match to it. It did not burn rapidly as celluloid does, andCraig seemed more than ever interested. MacLeod himself was no meandetective. Accustomed to action, he had an idea of what to do.

  "Wait here!" he called back, dashing out. "I'm going to the nearesthouse up the road for help. I'll be back in a moment."

  We heard him back and turn his car and shoot away. Meanwhile, Kennedywas looking over carefully Jackson's roadster. He tapped the gas-tankin the rear, then opened it. There was not a drop of gas in it. Helifted up the hood and looked inside at the motor. Whatever he sawthere, he said nothing. Finally, by siphoning some gas from Snedden'stank and making some adjustments, he seemed to have the car in acondition again for it to run. He was just about to start it whenMacLeod returned, carrying a canary-bird in a cage.

  "I've telephoned to town," he announced. "Some one will be here soonnow. Meanwhile, an idea occurred to me, and I borrowed this bird. Letme see whether the idea is any good."

  Kennedy, by this time, had started the engine. MacLeod placed thebright little songster near the stove on the work-bench and began towatch it narrowly.

  More than ever up in the air over the mystery, I could only watchKennedy and MacLeod, each following his own lines.

  It might, perhaps, have been ten minutes after MacLeod returned, andduring that time he had never taken his eyes off the bird, when I beganto feel a little drowsy. A word from MacLeod roused me.

  "There's carbon monoxide in the air, Kennedy!" he exclaimed. "You knowhow this gas affects birds."

  Kennedy looked over intently. The canary had begun to show evidentsigns of distress over something.

  "It must be that this stove is defective," pursued MacLeod, picking upthe poor little bird and carrying it quickly into the fresh air, whereit could regain its former liveliness. Then, when he returned, headded, "There must be some defect in the stove or the draught thatmakes it send out the poisonous gas."

  "There's some gas," agreed Kennedy. "It must have cleared away mostly,though, or we couldn't stand it ourselves."

  Craig continued to look about the car and the building, in the vainhope of discovering some other clue. Had Mrs. Snedden been killed bythe carbonic oxide? Was it a case of gas poisoning? Then, too, why hadshe been here at all? Who had shut her up? Had she been overcome firstand, in a stupor, been unable to move to save herself? Above all, whathad this to do with the mysterious phantom slayer that had wrecked somuch of the works in less than a week?

  It was quite late in the afternoon when, at last, people came from thetown and took away both the body of Mrs. Snedden and Jackson's car.Snedden could only stare and work his fingers, and after we had seenhim safely in the care of some one we could trust Kennedy, MacLeod, andI climbed into MacLeod's car silently.

  "It's too deep for me," acknowledged MacLeod. "What shall we do next?"

  "Surely that fellow must have my pictures developed by this time,"considered Kennedy. "Shoot back there."

  "They came out beautifully--all except one," reported the druggist, whowas somewhat of a camera fiend himself. "That's a wonderful system,sir."

  Kennedy thanked him for his trouble and took the prints. With care hepieced them together, until he had several successive panoramas of thecountry taken from various elevations of the parachute. Then, with amagnifying-glass, he went over each section minutely.

  "Look at that!" he pointed out at last with the sharp tip of a pencilon one picture.

  In what looked like an open space among some trees was a tiny figure ofa man. It seemed as if he were hacking at something with an ax. Whatthe something was did not appear in the picture.

  "I should say that it was half a mile, perhaps a mile, farther awaythan that grove," commented Kennedy, making a rough calculation.

  "On the old Davis farm," considered MacLeod. "Look and see if you can'tmake out the ruins of a house somewhere near-by. It was burned manyyears ago."

  "Yes, yes," returned Kennedy, excitedly; "there's the place! Do youthink we can get there in a car before it's dark?"

  "Easily," replied MacLeod.

  It was only a matter of minutes before we three were poking about in atangle of wood and field, seeking to locate the spot where Kennedy'sapparatus had photographed the lone axman.

  At last, in a large, cleared field, we came upon a most peculiar heapof debris. As nearly as I could make out, it was a pile of junk, butmost interesting junk. Practically all of it consisted in broken bitsof the celluloid-like stuff we had seen in the abandoned building.Twisted inextricably about were steel wires and bits of all sorts ofmaterial. In the midst of the wreckage was something that looked forall the world like the remains of a gas-motor. It was not rusted,either, which indicated that it had been put there recently.

  As he looked at it, Craig's face displayed a smile of satisfaction.

  "Looks as though it might have been an aeroplane of the tractor type,"he vouchsafed, finally.

  "Surely there couldn't have been an accident," objected MacLeod. "Noaviator could have lived through it, and there's no body."

  "No; it was purposely destroyed," continued Craig. "It was landed herefrom somewhere else for that purpose. That was what the man in thepicture was doing with the ax. After the last explosion somethinghappened. He brought the machine here to destroy the evidence."

  "But," persisted MacLeod, "if there had been an aeroplane hoveringabout we should have seen it in the air, passing over the works at thetime of the explosion."

  Kennedy picked the pieces, significantly.

  "Some one about here has kept abreast of the times, if not ahead. See;the planes were of this non-inflammable celluloid that made itvirtually transparent and visible only at a few hundred feet in theair. The aviator could fly low and so drop those pastillesaccurately--and unseen. The engine had one of those new muffler-boxes.He would have been unheard, too, except for that delicate air-shipdetector."

  MacLeod and I could but stare at each other, aghast. Without a doubt itwas in the old merry-go-round building that the phantom aviator hadestablished his hangar. What the connection was between the tragedy inthe Snedden family and the tragedy in the powder-works we did not know,but, at least, now we knew that there was some connection.

  It was growing dark rapidly, and, with some difficulty, we retraced oursteps to the point where we had left the car. We whirled back to thetown, and, of course, to the Snedden house.

  Snedden was sitting in the parlor when we arrived, by the body of hiswife, staring, speechless, straight before him, while several neighborswere gathered about, trying to co
nsole him. We had scarcely enteredwhen a messenger-boy came up the path from the gate. Both Kennedy andMacLeod turned toward him, expecting some reply to the numerousmessages of alarm sent out earlier in the afternoon.

  "Telegram for Mrs. Snedden," announced the boy.

  "MRS. Snedden?" queried Kennedy, surprised, then quickly: "Oh yes,that's all right. I'll take care of it."

  He signed for the message, tore it open, and read it. For a moment hisface, which had been clouded, smoothed out, and he took a couple ofturns up and down the hall, as though undecided. Finally he crumpledthe telegram abstractedly and shoved it into his pocket. We followedhim as he went into the parlor and stood for several moments, lookingfixedly on the strangely flushed face of Mrs. Snedden. "MacLeod," hesaid, finally, turning gravely toward us, and, for the present, seemingto ignore the presence of the others, "this amazing series of crimeshas brought home to me forcibly the alarming possibilities of applyingmodern scientific devices to criminal uses. New modes and processesseem to bring new menaces."

  "Like carbon-monoxide poisoning?" suggested MacLeod. "Of course it haslong been known as a harmful gas, but--"

  "Let us see," interrupted Kennedy. "Walter, you were there when Iexamined Jackson's car. There was not a drop of gasolene in the tank,you will recall. Even the water in the radiator was low. I lifted thehood. Some one must have tampered with the carburetor. It was adjustedso that the amount of air in the mixture was reduced. More than that, Idon't know whether you noticed it or not, but the spark and gas wereset so that, when I did put gasolene in the tank, I had but to turn theengine over and it went. In other words, that car had been standingthere, the engine running, until it simply stopped for want of fuel."He paused while we listened intently, then resumed. "The gas-engine andgas-motor have brought with them another of those unanticipated menacesof which I spoke. Whenever the explosion of the combustible mixture isincomplete or of moderated intensity a gas of which little is known maybe formed in considerable quantities.

  "In this case, as in several others that have come to my attention,vapors arising from the combustion must have emitted certain noxiousproducts. The fumes that caused Ida Snedden's death were not of carbonmonoxide from the stove, MacLeod. They were splitting-products ofgasolene, which are so new to science that they have not yet been named.

  "Mrs. Snedden's death, I may say for the benefit of the coroner, wasdue to the absorption of some of these unidentified gaseous poisons.They are as deadly as a knife-thrust through the heart, under certainconditions. Due to the non-oxidation of some of the elements ofgasolene, they escape from the exhaust of every running gas-engine. Inthe open air, where only a whiff or two would be inhale now and then,they are not dangerous. But in a closed room they may kill in anincredibly short time. In fact, the condition has given rise to anentirely new phenomenon which some one has named 'petromortis.'"

  "Petromortis?" repeated Snedden, who, for the first time, began to showinterest in what was going on about him. "Then it was an accident?"

  "I did not say it was an accident," corrected Craig. "There is an oldadage that murder will out. And this expression of human experience isonly repeated in what we modern scientific detectives are doing. No manbent on the commission of a crime can so arrange the circumstances ofthat crime that it will afterward appear, point by point, as anaccident."

  Kennedy had us all following him breathlessly now.

  "I do not consider it an accident," he went on, rapidly piecingtogether the facts as we had found them. "Ida Snedden was killedbecause she was getting too close to some one's secret. Even atluncheon, I could see that she had discovered Gertrude's attachment forGarretson. How she heard that, following the excitement of theexplosion this afternoon, Gertrude and Garretson had disappeared, I donot pretend to know. But it is evident that she did hear, that she wentout and took Jackson's car, probably to pursue them. If we have heardthat they went by the river road, she might have heard it, too.

  "In all probability she came along just in time to surprise some oneworking on the other side of the old merry-go-round structure. Therecan be no reason to conceal the fact longer. From that desertedbuilding some one was daily launching a newly designed invisibleaeroplane. As Mrs. Snedden came along, she must have been just in timeto see that person at his secret hangar. What happened I do not know,except that she must have run the car off the river road and into thebuilding. The person whom she found must have suddenly conceived amethod of getting her out of the way and making it look like anaccident of some kind, perhaps persuaded her to stay in the car withthe engine running, while he went off and destroyed the aeroplane whichwas damning evidence now."

  Startling as was the revelation of an actual phantom destroyer, ourminds were more aroused as to who might be the criminal who hademployed such an engine of death.

  Kennedy drew from his pocket the telegram which had just arrived, andspread it out flat before us on a table. It was dated Philadelphia, andread:

  MRS. IDA SNEDDEN, Nitropolis:

  Garretson and Gertrude were married to-day. Have traced them to theWolcott. Try to reconcile Mr. Snedden.

  HUNTER JACKSON.

  I saw at once that part of the story. It was just a plain love-affairthat had ended in an elopement at a convenient time. The fire-eatingGarretson had been afraid of the Sneddens and Jackson, who was theirfriend. Before I could even think further, Kennedy had drawn out thefilms taken by the rocket-camera.

  "With the aid of a magnifying-glass," he was saying, "I can get justenough of the lone figure in this picture to identify it. These are thecrimes of a crazed pacifist, one whose mind had so long dwelt on thehorrors of--"

  "Look out!" shouted MacLeod, leaping in front of Kennedy.

  The strain of the revelation had been too much. Snedden--a ravingmaniac--had reeled forward, wildly and impotently, at the man who hadexposed him.