"But I should like to have a chance to investigate."
"There may be some connection with the fire," hinted Gaskell anxiously as he accompanied us to the door.
At our own apartment, when we returned, we found our friend, Burke, of the Secret Service, waiting for us.
"Just had a hurry call to come to New York," he explained, "and thought I'd like to drop in on you first."
"What's the trouble?" asked Kennedy.
"Why, there's been a mysterious yacht lurking about the mouth of the harbor for several days and they want to look into it."
"Whose yacht do they think it is?"
"They don't know, but it is said to resemble one that belongs to a man named Gaskell."
"Gaskell?" repeated Craig, turning suddenly.
"Yes,—the Furious—a fast, floating palace—one of these new power yachts, run by a gas engine—built for speed. Why, do you know anything about it?"
Kennedy said nothing.
"The revenue cutter Uncas has been assigned to me," went on Burke. "If you have nothing better to do, I'd like to have you give me a hand in the case. You might find it a little different from the ordinary run."
"I shall be glad to go with you," replied Craig cordially. "Only, just now I've got a particular case of my own. I'll see you tomorrow at the Customs House, though, if I can."
"Good!" exclaimed Burke. "I don't think either of you, particularly Jameson, will regret it. It promises to be a good story."
Burke had scarcely left us when Kennedy decided on his next move. We went directly over to the Long Island Railroad station and caught the next train out to Oceanhurst, not a long run from the city.
Thus, early in the evening, Kennedy was able to begin, under cover, his investigation of the neighborhood of the Rovigno and Gaskell houses.
We entered the Gaskell estate and looked it over as we made our way toward the stable to find the groom. Out on the bay we could see the Furious at anchor. Nearer in shore were a couple of Count Rovigno's speedy racing motor-boats. Along the shore, we saw a basin for yachts, capable even of holding the Furious.
The groom proved to be a rather dull-witted fellow, and left us pretty much to our own devices.
"Ya-as—sparks—I saw 'em," he drawled in answer to Kennedy's question. "So did Mr. Gaskell. Naw—I don't know nawthin' about 'em."
He had lumbered out into another part of the stable when I heard a low exclamation from Craig, of "Look, Walter!"
I did look in amazement. There were indeed little sparks, in fact a small burst of them in all directions, where there were metal surfaces in close proximity to one another.
Kennedy had brought along with him a strange instrument and he was now looking attentively at it.
"What is that?" I asked.
"The bolometer," he replied, "invented by Professor Langley."
"And what does it do?"
"Detects waves," he replied, "rays that are invisible to the eye. For instance, just now it tells me that shooting through the darkness are invisible waves, perhaps infra-red rays."
He paused, and I looked at him inquiringly.
"You know," he explained, "the infra-red rays are closer to the heat rays than those of the upper end of the spectrum and beyond, the ultra-violet rays, with which we have already had some experience."
Kennedy continued to look at his bolometer. "Yes," he remarked thoughtfully, half to himself, "somewhere around here there is a generator of infra-red rays and a projector of those rays. It reminds me of those so-called F-rays of Ulivi—or at least of a very powerful wireless."
I was startled at the speculations that his words conjured up in my mind. Was the "evil eye" of superstition a scientific fact? Was there a baneful beam that could be directed at will—one that could not be seen or felt until it worked its havoc? Was there a power that steel walls could not hold, which, in fact, was the more surely transmitted by them?
Somehow, the fact of the strange disappearance of Petzka, the wireless operator, kept bobbing up in my mind. I could not help wondering whether, perhaps, he had found this strange power and was using it for some nefarious purpose. Could it have been Petzka who was responsible for the fires? But, why? I could not figure it out.
Early the next morning we called at the Gaskell town house again. Kennedy had brought with him a small piece of apparatus which seemed to consist of two sets of coils placed on ends of a magnet bar. To them was attached a long flexible wire which he screwed into an electric light bulb socket. Then he placed a peculiar telephone-like apparatus, attached to the other end, to his ears. He adjusted the magnets and carried the thing carefully about the room.
At one point he stopped and moved the thing vertically up along the wall, from floor to ceiling.
"That's a gas pipe," he said simply.
"What's the instrument?" I asked.
"A new apparatus for finding pipes electrically, which I think can be just as well applied to finding other things concealed in walls under plaster and paper."
He paused to adjust the thing. "The electrical method," he went on, "is a special application of well-known induction balance principles. You see one set of coils receives an alternating or vibrating current. The other is connected with this telephone. First I established a balance so that there was no sound in the telephone."
He moved the thing about. "Now, when the device comes near metal-piping, for example, or a wire, the balance is disturbed and I hear a sound. That was the gas pipe. It is easy to find its exact location. Hulloa—"
He paused again in a corner, back of Gaskell's desk and appeared to be listening intently.
A moment later he was ruthlessly breaking through the plaster of the beautifully decorated wall.
Sure enough, in there was a detectaphone, concealed only a fraction of an inch beneath the paper, with wires leading down inside the partition in the direction of the cellar.
Chapter XI
The Infernal Machines
He ripped the little mechanical eavesdropper out, wires and all, but he did not disconnect the wires, yet.
We traced it out, and down into the cellar the wires led, directly, and then across, through a small opening in the foundations into the next cellar of an apartment house, ending in a bin or storeroom.
In itself the thing, so far, gave no clew as to who was using it or the purpose for which it had been installed. But it was strange.
"Someone was evidently trying to get something from you, Mr. Gaskell,"
