"To protect me from the effects of the black lamp."

"What is the black lamp?"

"I don't know exactly. Saranoff invented it. It gives a black light and it kills all other light except sunlight, and it paralyses the brain."

"Did you know that the model of the Breslau gun had been stolen?"

"Yes."

"What were you going to do after you were rescued from jail?"

"I was going to make a full-sized gun. We have a disappearing gun platform built in the swamps at the juncture of the Potomac and Piscataway Creek. The gun was to be mounted there and we would sh.e.l.l Washington and inst.i.tute a reign of terror. It would be a signal for uprisings all over the country."

"Is there a black lamp at that gun platform?"

"Yes. The black lamp will kill both the flash and the report."

"Where did you get the formula for radite?"

"We got it from one of Dr. Bird's a.s.sistants. His name--"

As he spoke the last few sentences, Karuska's voice had steadily risen almost to a shriek. As he endeavored to give the name of the doctor's treacherous helper his voice changed to an unintelligible screech and then died away into silence. Major Martin stepped forward and bent over the p.r.o.ne figure. Hurriedly he tore away the electrical connections and placed a stethoscope over the Russian's heart. He listened for a moment and then straightened up, his face pale.

"I hope that the information you obtained is worth a life, Dr. Bird,"

he said, his voice trembling slightly, "because it has cost one."

"It may easily save thousands of lives. I thank you, Major, and I will see that no blame attaches to you for your actions. I only wish that he had lived long enough to tell me the name of my a.s.sistant who has sold me to Saranoff. However, we'll get that information in other ways. Carnes, telephone Lawson at Atlanta to slam O'Grady into a cell pending investigation while I get Camp Meade on the wire and order up a couple of tanks. We are going to attack that gun emplacement at daybreak."

The telephone bell in the laboratory jangled sharply. Major Martin answered it and turned to Carnes.

"You're wanted on the telephone, Mr. Carnes."

The detective stepped forward and took the transmitter.

"Carnes speaking," he said. "Yes. Oh, h.e.l.lo, Bolton. Yes, we have Karuska here, or rather his body. Yes, Dr. Bird is here right now.

You've what? Great Scott, wait a minute."

"Dr. Bird," he cried eagerly turning from the telephone, "Bolton has located the Washington headquarters of the Young Labor party."

Dr. Bird sprang to the instrument.

"Bird speaking, Bolton," he cried. "You've located their headquarters?

Who's running it? Stanesky, eh? You're on the right track; he used to be Saranoff's right hand man. Where is the place located? I don't seem to recollect the spot. You have it well surrounded? Where are you speaking from? All right, we'll join you as quickly as we can. Keep your patrols out and don't let anyone get away."

He hung up the receiver and turned to Carnes.

"Did you have the car wait?" he asked. "Good enough; we'll jump for the Bureau and pick up all the vitrilene laying around loose and then join Bolton. He thinks that he has the whole outfit bottled up."

Bolton was waiting as the car rolled up and Dr. Bird leaped out.

"Where are they?" demanded the doctor eagerly.

"In an abandoned factory building about three hundred yards from here," replied the Chief of the Secret Service. "I traced them through New York. We have been watching the place ever since yesterday noon, and I know that Stanesky is in there with half a dozen others. No one has tried to leave since we set our watch. One funny thing has happened. About an hour ago a peculiar red glow suffused the whole building. It has died down a good deal since, but we can still see it through the windows. Could you tell us what it means?"

"No. I couldn't, Bolton, but we'll find out. How many men have you?"

"I have sixteen stationed around."

"That's more than we'll need. I have only vitrilene shields and helmets enough to equip six men. Pick out your three best men to go with us and we'll make a try at entering."

Bolton strode off into the darkness and returned in a few moments with three men at his heels. Dr. Bird spoke briefly to the operatives, all of them men who had been his companions on other adventures. He explained the need for the vitrilene helmets and shields, and without comment the six donned their armor and followed Bolton as he strode toward the building. As they approached, a dull red glow could be plainly seen through the windows, and Dr. Bird paused and studied the phenomenon for a moment.

"I don't know what that means, Bolton," he said softly, "but I don't like the looks of it. Stanesky is up to some devilment or other. I wouldn't be a bit surprised to find out that he knows all about your pickets and is ready for a raid."

"We'd better rush the place, then," muttered Bolton.

Dr. Bird nodded agreement and with a sharp command to his men Bolton broke into a run. Not a shot was fired as they approached, and the front door gave readily to Bolton's touch. At it opened there came a grating sound from the roof followed by the whir of a propeller. Dr.

Bird ran out of the building and glanced up.

"A helicopter!" he cried. "They were expecting us and have escaped!"

He drew his pistol and fired ineffectually at the great bird-like ship which was rising almost noiselessly into the air. He cursed and turned again to the building.

Bolton still stood in the room which they had first entered. His flashlight showed it to be empty, but from under a door on the opposite side a line of dull red light glowed evilly. With his pistol ready in his hand, Bolton approached the door on hands and knees.

When he reached it he threw his shoulder against it and dropped flat to the floor as the door swung open. No shot greeted him, and he stared for a moment and then rose to his feet.

"Nothing in here but some gla.s.s statues," he announced.

Dr. Bird followed him into the room. As he looked at what Bolton had called gla.s.s statues he gasped and shielded his eyes.

"G.o.d in Heaven!" he e.j.a.c.u.l.a.t.ed. "Those were living men!"

Before them were three men or what had been three men. All stood in strained att.i.tudes with a look of horror frozen on their faces. The thing that made the spectators shudder was that their bodies had, by some diabolical method, been rendered semi-transparent. The dull red light which suffused the room emanated from the three bodies. Dr. Bird examined them closely, being careful not to touch them.

"The ident.i.ty of my treacherous a.s.sistant is known," he said grimly as he pointed at the middle figure. "It was Gerond. What is this?"

He took an envelope from the hand of the middle figure and opened it.

A sheet of paper fell out and he picked it up and read it.

"My dear Mr. Bolton," ran the note. "Your methods of tracing and picketing my headquarters are so crude as to be almost laughable. This base has served its purpose and we were ready to abandon it in any event, but I couldn't resist the temptation to let you almost nab us.

The three men whom you will find here are agents who failed in their duty. If you are interested in learning the method of their execution, you might take to heart the words of your colleague, Dr. Bird: 'The clue lies in those windows.'"