If there were any thoughts like these pa.s.sing through Kennedy's mind he did not show it, at least not in the shape of hesitating in the course he had evidently mapped out to follow. He said little, but hurried off from the studio in a cab up-town again to the laboratory. A few minutes later we were speeding down to the museum.

There was not much time for Craig to work if he hoped to be ready for anything that might happen that night. He began by winding coil after coil of copper wire about the storeroom in the bas.e.m.e.nt of the museum.

It was not a very difficult matter to conceal it, so crowded was the room, or to lead the ends out through a window at the opposite side from that where the window had been broken open.

Up-stairs in the art-gallery he next installed several boxes such as those which I had seen him experimenting with during his tests of selenium on the afternoon when Mr. Spencer had first called on us. They were camera-like boxes, about ten inches long, three inches or so wide, and four inches deep.

One end was open, or at least looked as though the end had been shoved several inches into the interior of the box. I looked into one of the boxes and saw a slit in the wall that had been shoved in. Kennedy was busy adjusting the apparatus, and paused only to remark that the boxes contained two sensitive selenium surfaces balanced against two carbon resistances. There was also in the box a clockwork mechanism which Craig wound up and set ticking ever so softly. Then he moved a rod that seemed to cover the slit, until the apparatus was adjusted to his satisfaction, a delicate operation, judging by the care he took.

Several of these boxes were installed, and by that time it was quite late.

Wires from the apparatus in the art-gallery also led outside, and these as well as the wires from the coils down in the bas.e.m.e.nt he led across the bit of garden back of the Spencer house and up to a room on the top floor. In the upper room he attached the wires from the storeroom to what looked like a piece of crystal and a telephone receiver. Those from the art-gallery terminated in something very much like the apparatus which a wireless operator wears over his head.

Among other things which Craig had brought down from the laboratory was a package which he had not yet unwrapped. He placed it near the window, still wrapped. It was quite large, and must have weighed fifteen or twenty pounds. That done, he produced a tape-measure and began, as if he were a surveyor, to measure various distances and apparently to calculate the angles and distances from the window-sill of the Spencer house to the skylight, which was the exact centre of the museum. The straight distance, if I recall correctly, was in the neighborhood of four hundred feet.

These preparations completed, there was nothing left to do but to wait for something to happen. Spencer had declined to get alarmed about our fears for his own safety, and only with difficulty had we been able to dissuade him from moving heaven and earth to find Miss White, a proceeding which must certainly have disarranged Kennedy's carefully laid plans. So interested was he that he postponed one of the most important business conferences of the year, growing out of the anti-trust suits, in order to be present with Dr. Lith and ourselves in the little upper back room.

It was quite late when Kennedy completed his hasty arrangements, yet as the night advanced we grew more and more impatient for something to happen. Craig was apparently even more anxious than he had been the night before, when we watched in the art-gallery itself. Spencer was nervously smoking, lighting one cigar furiously from another until the air was almost blue.

Scarcely a word was spoken as hour after hour Craig sat with the receiver to his ear, connected with the coils down in the storeroom.

"You might call this an electric detective," he had explained to Spencer. "For example, if you suspected that anything out of the way was going on in a room anywhere this would report much to you even if you were miles away. It is the discovery of a student of Thorne Baker, the English electrical expert. He was experimenting with high-frequency electric currents, investigating the nature of the discharges used for electrifying certain things. Quite by accident he found that when the room on which he was experimenting was occupied by some person his measuring-instruments indicated that fact. He tested the degree of variation by pa.s.sing the current first through the room and then through a sensitive crystal to a delicate telephone receiver. There was a distinct change in the buzzing sound heard through the telephone when the room was occupied or unoccupied. What I have done is to wind single loops of plain wire on each side of that room down there, as well as to wind around the room a few turns of concealed copper wire. These collectors are fitted to a crystal of carborundum and a telephone receiver."

We had each tried the thing and could hear a distinct buzzing in the receiver.

"The presence of a man or woman in that room would be evident to a person listening miles away," he went on. "A high-frequency current is constantly pa.s.sing through that storeroom. That is what causes that normal buzzing."

It was verging on midnight when Kennedy suddenly cried: "Here, Walter, take this receiver. You remember how the buzzing sounded. Listen. Tell me if you, too, can detect the change."

I clapped the receiver quickly to my ear. Indeed I could tell the difference. In place of the load buzzing there was only a mild sound.

It was slower and lower.

"That means," he said excitedly, "that some one has entered that pitch-dark storeroom by the broken window. Let me take the receiver back again. Ah, the buzzing is coming back. He is leaving the room. I suppose he has found the electric light cane and the pistol where he left them. Now, Walter, since you have become accustomed to this thing take it and tell me what you hear."

Craig had already seized the other apparatus connected with the art-gallery and had the wireless receiver over his head. He was listening with rapt attention, talking while he waited.

"This is an apparatus," he was saying, "that was devised by Dr.

Fournier d'Albe, lecturer on physics at Birmingham University, to aid the blind. It is known as the optophone. What I am literally doing now is to HEAR light. The optophone translates light into sound by means of that wonderful little element, selenium, which in darkness is a poor conductor of electricity, but in light is a good conductor. This property is used in the optophone in transmitting an electric current which is interrupted by a special clockwork interrupter. It makes light and darkness audible in the telephone. This thing over my head is like a wireless telephone receiver, capable of detecting a current of even a quarter of a microampere."

We were all waiting expectantly for Craig to speak. Evidently the intruder was now mounting the stairs to the art-gallery.

"Actually I can hear the light of the stars shining in through that wonderful plate gla.s.s skylight of yours, Mr. Spencer," he went on. "A few moments ago when the moon shone through I could hear it, like the rumble of a pa.s.sing cart. I knew it was the moon both because I could see that it must be shining in and because I recognised the sound. The sun would thunder like a pa.s.sing express-train if it were daytime now.

I can distinguish a shadow pa.s.sing between the optophone and the light.

A hand moved across in front of it would give a purring sound, and a glimpse out of a window in daylight would sound like a cinematograph reeling off a film.

"Ah, there he is." Craig was listening with intense excitement now.

"Our intruder has entered the art-gallery. He is flashing his electric light cane about at various objects, reconnoitring. No doubt if I were expert enough and had had time to study it, I could tell you by the sound just what he is looking at."

"Craig," I interrupted, this time very excited myself, "the buzzing from the high-frequency current is getting lower and lower."

"By George, then, there is another of them," he replied. "I'm not surprised. Keep a sharp watch. Tell me the moment the buzzing increases again."

Spencer could scarcely control his impatience. It had been a long time since he had been a mere spectator, and he did not seem to relish being held in check by anybody.

"Now that you are sure the vandal is there," he cut in, his cigar out in his excitement, "can't we make a dash over there and get him before he has a chance to do any more damage? He might be destroying thousands of dollars' worth of stuff while we are waiting here."

"And he could destroy the whole collection, building and all, including ourselves into the bargain, if he heard so much as a whisper from us,"

added Kennedy firmly.

"That second person has left the storeroom, Craig," I put in. "The buzzing has returned again full force."

Kennedy tore the wireless receiver from his ear. "Here, Walter, never mind about that electric detective any more, then. Take the optophone.

Describe minutely to me just exactly what you hear."

He had taken from his pocket a small metal ball. I seized the receiver from him and fitted it to my ear. It took me several instants to accustom my ears to the new sounds, but they were plain enough, and I shouted my impressions of their variations. Kennedy was busy at the window over the heavy package, from which he had torn the wrapping. His back was toward us, and we could not see what he was doing.

A terrific din sounded in my ears, almost splitting my ear-drums. It was as though I had been suddenly hurled into a magnified cave of the winds and a cataract mightier than Niagara was thundering at me. It was so painful that I cried out in surprise and involuntarily dropped the receiver to the floor.

"It was the switching on of the full glare of the electric lights in the art-gallery," Craig shouted. "The other person must have got up to the room quicker than I expected. Here goes."

A loud explosion took place, apparently on the very window-sill of our room. Almost at the same instant there was a crash of gla.s.s from the museum.

We sprang to the window, I expecting to see Kennedy injured, Spencer expecting to see his costly museum a ma.s.s of smoking ruins. Instead we saw nothing of the sort. On the window-ledge was a peculiar little instrument that looked like a miniature field-gun with an elaborate system of springs and levers to break the recoil.

Craig had turned from it so suddenly that he actually ran full tilt into us. "Come on," he cried breathlessly, bolting from the room, and seizing Dr. Lith by the arm as he did so. "Dr. Lith, the keys to the museum, quick! We must get there before the fumes clear away."

He was taking the stairs two at a time, dragging the dignified curator with him.

In fewer seconds than I can tell it we were in the museum and mounting the broad staircase to the art-gallery. An overpowering gas seemed to permeate everything.

"Stand back a moment," cautioned Kennedy as we neared the door. "I have just shot in here one of those asphyxiating bombs which the Paris police invented to war against the Apaches and the motor-car bandits.

Open all the windows back here and let the air clear. Walter, breathe as little of it as you can--but--come here--do you see?--over there, near the other door--a figure lying on the floor? Make a dash in after me and carry it out. There is just one thing more. If I am not back in a minute come in and try to get me."

He had already preceded me into the stifling fumes. With a last long breath of fresh air I plunged in after him, scarcely knowing what would happen to me. I saw the figure on the floor, seized it, and backed out of the room as fast as I could.

Dizzy and giddy from the fumes I had been forced to inhale, I managed to drag the form to the nearest window. It was Lucille White.

An instant later I felt myself unceremoniously pushed aside. Spencer had forgotten all about the millions of dollars' worth of curios, all about the suspicions that had been entertained against her, and had taken the half-conscious burden from me.

"This is the second time I have found you here, Edouard," she was muttering in her half-delirium, still struggling. "The first time--that night I hid in the mummy-case, you fled when I called for help. I have followed you every moment since last night to prevent this. Edouard, don't, DON'T! Remember I was--I am your wife. Listen to me. Oh, it is the absinthe that has spoiled your art and made it worthless, not the critics. It is not Mr. Spencer who has enticed me away, but you who drove me away, first from Paris, and now from New York. He has been only--No! No!--" she was shrieking now, her eyes wide open as she realised it was Spencer himself she saw leaning over her. With a great effort she seemed to rouse herself. "Don't stay. Run--run. Leave me. He has a bomb that may go off at any moment. Oh--oh--it is the curse of absinthe that pursues me. Will you not go? Vite! Vite!"

She had almost fainted and was lapsing into French, laughing and crying alternately, telling him to go, yet clinging to him.

Spencer paid no attention to what she had said of the bomb. But I did.

The minute was up, and Kennedy was in there yet. I turned to rush in again to warn him at any peril.

Just then a half-conscious form staggered against me. It was Craig himself. He was holding the infernal machine of the five gla.s.s tubes that might at any instant blow us into eternity.

Overcome himself, he stumbled. The sinking sensation in my heart I can never describe. It was just a second that I waited for the terrific explosion that was to end it all for us, one long interminable second.

But it did not come.