Here we were, locked in a little room on the top floor of the mysterious house. I looked out of both windows. There was no way to climb down and it was too far to jump, especially in the uncertain darkness. I threw myself at the door. It had been effectually braced by our captors.

Garrick, in the meantime, had lighted the light again, and placed it by the window.

Forbes, now partly recovered, was rambling along, and Garrick, with one eye on him and the other on something which he was working over in the light, was too busy to pay much attention to my futile efforts to find a means of escape.

At first we could not make out what it was that Forbes was trying to tell us, but soon, as the fresh air in the room revived him, his voice became stronger. Apparently he recognised us and was trying to offer an explanation of his presence here.

"He kidnapped me—brought me here," Forbes was muttering. "Three days—I've been shut up in this room."

"Who brought you here?" I demanded sharply.

"I don't know his name—man at the gambling place—after the raid—said he'd take me in his car somewhere—from the other place back of it—last I remember—must have drugged me—woke up here—all I know."

"You've been a prisoner, then?" I queried.

"Yes," he murmured.

"A likely story," I remarked, looking questioningly at Garrick who had been listening but had not ceased his own work, whatever it was. "What are you going to do, Guy? We can't stay here and waste time over such talk as this while they are escaping. They must be almost to the road now, and turning down in the opposite direction from Dillon and his man."

Garrick said nothing. Either he was too busy solving our present troubles or he was, like myself, not impressed by Forbes' incoherent story. He continued to adjust the little instrument which I had seen him draw from his pocket and now recognised as the thing which looked like a telephone transmitter. Only, the back of it seemed to gleam with a curious brightness under the rays of the light, as he handled it.

"They have somehow contrived to escape the effect of the bombs," he was saying, "and have surprised us in the room on the top floor where the light is. We are up here with a young fellow named Forbes, whom we have captured. He's the young man that I saw several times at the gambling joint and was at dinner with Warrington the night when the car was stolen. He was pretty badly overcome by the fumes, but I've brought him around. He either doesn't know much or won't tell what he knows. That doesn't make any difference now, though. They have escaped in a car. They are leaving by the road. Wait. I'll see whether they have reached it yet. No, it's too dark to see and they have no light on the car. But they must have turned. They said they were going in the direction opposite from you."

"Well?" I asked, mystified. "What of it? I know all that, already."

"But Dillon doesn't," replied Garrick, in great excitement now. "I knew that we should have to have some way of communicating with him instantly if this fellow proved to be as resourceful as I believed him to be. So I thought of the radiophone or photophone of Dr. Alexander Graham Bell. I have really been telephoning on a beam of light."

"Telephoning on a beam of light?" I repeated incredulously.

"Yes," he explained, feeling now at liberty to talk since he had delivered his call for help. "You see, I talk into this transmitter. The simplest transmitter for this purpose is a plane mirror of flexible material, silvered mica or microscope glass. Against the back of this mirror my voice is directed. In the carbon transmitter of the telephone a variable electrical resistance is produced by the pressure on the diaphragm, based on the fact that carbon is not as good a conductor of electricity under pressure as when not. Here, the mouthpiece is just a shell supporting a thin metal diaphragm to which the mirror on the back is attached, an apparatus for transforming the air vibrations produced by the voice into light vibrations of the projected beam, which is reflected from this light here in the room. The light reflected is thus thrown into vibrations corresponding to those in the diaphragm."

"And then?" I asked impatiently.

"That varying beam of light shoots out of this room, and is caught by the huge reflector which you saw me set up at the foot of that tall tree which you can just see against the dark sky over there. That parabolic mirror gathers in the scattered rays, focusses them on the selenium cell which you saw in the middle of the reflector, and that causes the cell to vary the amount of electric current passing through it from a battery of storage cells. It is connected with a very good telephone receiver. Every change in the beam of light due to the vibrations of my voice is caught by that receiving mirror, and the result is that the diaphragm in the receiver over there which Dillon is holding to his ear responds. The thing is good over several hundred yards, perhaps miles, sometimes. Only, I wish it would work both ways. I would like to feel sure that Dillon gets me."

I looked at the simple little instrument with a sort of reverence, for on it depended the momentous question of whether we should be released in time to pursue the two who were escaping in the automobile.

"You'll have to hurry," continued Garrick, speaking into his transmitter. "Give the signal. Get the car ready. Anything, so long as it is action. Use your own judgment."

There he was, flashing a message out of our prison by an invisible ray that shot across the Cimmerian darkness to the point where we knew that our friends were waiting anxiously. I could scarcely believe it. But Garrick had the utmost faith in the ability of the radiophone to make good.

"They MUST have started by this time," he cried, craning his neck out of the window and looking in every direction.

Forbes was still rambling along, but Garrick was not paying any attention to him. Instead, he began rummaging the room for possible evidence, more for something to do than because he hoped to find anything, while we were waiting anxiously for something to happen.

An exclamation from Garrick, however, brought me to his side. Tucked away in a bureau drawer under some soiled linen that plainly belonged to Forbes, he drew out what looked like a single blue-steel tube about three inches long. At its base was a hard-rubber cap, which fitted snugly into the palm of the hand as he held it. His first and middle fingers encircled the barrel, over a steel ring. A pull downward and the thing gave a click.

"Good that it wasn't loaded," Garrick remarked. "I knew what the thing was, all right, but I didn't think the spring was as delicate as all that. It is a new and terrible weapon of destruction of human life, one that can be carried by the thug or the burglar and no one be the wiser, unless he has occasion to use it. It is a gun that can be concealed in the palm of the hand. A pull downward on that spring discharges a thirty-two calibre, centre fire cartridge. The most dangerous feature of it is that the gun can be carried in an upper vest pocket as a fountain pen, or in a trousers pocket as a penknife."

I looked with added suspicion now, if not a sort of respect, on the young man who was tossing, half conscious, on the bed. Was he, after all, not the simple, gullible Forbes, but a real secret master of crime?

Garrick, keen though he had been over the discovery, was in reality much more interested just now in the result of his radiophone message. What would be the outcome?

I had been startled to see that almost instantly after his second call over the radiophone there seemed to rise on all sides of us lights and the low baying of dogs.

"What's all that?" I asked Garrick.

"Dillon had a dozen or so police dogs shipped up here quietly," answered Garrick, now straining his eyes and ears eagerly. "He started them out each in charge of an officer as soon as they arrived. I hope they had time to get around in that other direction and close in. That was what he sent the chauffeur back to see about, to make sure that they were placed by the man who is the trainer of the pack."

"What kind of dogs are they?"

"Some Airedales, but mostly Belgian sheep dogs. There is one in the pack, Cherry, who has a wonderful reputation. A great deal depends, now, on our dog-detectives."

"But," I objected, "what good will they be? Our men are in an automobile."

"We thought of that," replied Garrick confidently. "Here they are, at last," he cried, as a car swung up the lane from the road and stopped with a rush under our window. He leaned out and shouted, "Dillon—up here—quick!"

It was Dillon and his chauffeur, Jim. A moment later there was a tremendous shifting and pulling of heavy pieces of furniture in the hall, and, as the door swung open, the honest face of the commissioner appeared, inquiring anxiously if we were all right.

"Yes, all right," assured Garrick. "Come on, now. There isn't a minute to lose. Send Jim up here to take charge of Forbes. I'll drive the car myself."

Garrick accomplished in seconds what it takes minutes to tell. The chauffeur had already turned the car around and it was ready to start. We jumped in, leaving him to go upstairs and keep the manacled Forbes safely.

We gained the road and sped along, our lights now lighted and showing us plainly what was ahead. The dust-laden air told us that we were right as we turned into the narrow crossroad. I wondered how we were ever going to overtake them after they had such a start, at night, too, over roads which were presumably familiar to them.

"Drive carefully," shouted Dillon soon, "it must be along here, somewhere, Garrick."

A moment before we had been almost literally eating the dust the car ahead had raised. Garrick slowed down as we approached a bend in the road.

There, almost directly in our path, stood a car, turned half across the road and jammed up into a fence. I could scarcely believe it. It was the bandit's car—deserted!

"Good!" exclaimed Dillon as Garrick brought our own car to a stop with a jerk only a few feet away.

I looked about in amazement, first at the empty car and then into the darkness on either side of the road. For the moment I could not explain it. Why had they abandoned the car, especially when they had every prospect of eluding us in it?

They had not been forced to turn out for anybody, for no other vehicle had passed us. Was it tire trouble or engine trouble? I turned to the others for an explanation.

"I thought it must be about here," cried Dillon. "We had one of my men place an obstruction in the road. They didn't run into it, which shows clever driving, but they had to turn so sharply that they ran into the fence. I guess they realised that there was no use in turning and trying to go back."

"They have taken to the open country," shouted Garrick, leaping up on the seat of our car and looking about in a vain endeavour to catch some sign of them.

All was still, save here and there the sharp, distant bark of a dog.

"I wonder which way they went?" he asked, looking down at us.