falling into an immense void. His head slumped forward on his chest and Slavatsky shut off the generator.
"On the table," he said briefly.
Four men picked up the herculean frame of the unconscious doctor and hoisted him up on the table. Carson seized his head and bent it forward and the dwarf took from a case a syringe with a five-inch needle. He touched the point of it to the base of the doctor's brain.
"Slavatsky! Look!" cried Frink.
With an exclamation of impatience the dwarf turned and stared at a disc set on the wall of the cave. It was glowing brightly. With an oath he dropped the syringe and snapped a switch, plunging the cave into darkness. A tiny panel in the door opened to his touch and he stared out into the light.
"Soldiers!" he gasped. "Quick, the back way!"
As he spoke there came a sound as of a heavy body falling at the back of the cave. Slavatsky turned the switch and flooded the cave with light. At the back of the cave stood Operative Carnes, an automatic pistol in his hand.
"Open the main door!" Carnes snapped.
Slavatsky made a move toward the light, and Carnes' gun roared deafeningly in the confined space. The heavy bullet smashed into the wall an inch from the dwarf's hand and he started back.
"Open the main door!" ordered Carnes again.
The men stared at one another for a moment and the dwarf's eyes fell.
"Open the door, Frink," he said.
Frink moved over to a lever. He glanced at Slavatsky and a momentary gleam of intelligence passed between them. Frink raised his hand toward the lever and Carnes gun roared again and Frink's arm fell limp from a smashed shoulder.
"Slavatsky," said Carnes sternly, "come here!"
Slowly the dwarf approached.
"Turn around!" said Carnes.
He turned and felt the cold muzzle of Carnes' gun against the back of his neck.
"Now tell one of your men to open the door," said the detective. "If he promptly obeys your order, you are safe. If he doesn't, you die."
Slavatsky hesitated for a moment, but the cold muzzle of the automatic bored into the back of his neck and when he spoke it was in a quavering whine.
"Open the door, Carson," he whimpered.
There was moment of pause.
"If that door isn't open by the time I count three," said Carnes, " – as far as Slavatsky is concerned, it's just too bad. I'll have four shots left – and I'm a dead shot at this range. One! Two!"
His lips framed the word "three" and his fingers were tightening on the trigger when Carson jumped forward with an oath. He pulled a lever on the wall and the door swung open. Carnes shouted and through the opened door came a half dozen marines followed by an officer.
"Tie these men up!" snapped Carnes.
In a trice the six men were securely bound and Frink's bleeding shoulder was being skilfully treated by two of the marines. Carnes turned his attention to the unconscious doctor.
He rolled him over on his back and began to chafe his hands. An officer in a naval uniform came through the door and with a swift glance around, bent over Dr. Bird. He raised one of the doctor's eyelids and peered closely at his eye and then sniffed at his breath.
"It's some anesthetic I don't know," he said. "I'll try a stimulant."
He reached in his pocket for a hypodermic, but Carnes interrupted him.
"Earlier in the evening Dr. Bird said they were using lethane," he said.
"Oh, that new gas the Chemical Warfare Service has discovered," said the surgeon. "In that case I guess it'll just have to wear off. I know of nothing that will neutralize it."
Without replying, Carnes began to feverishly search the pockets of the unconscious scientist. With an exclamation of triumph he drew out a bottle and uncorked it. A strong smell as of garlic penetrated the room and he held the opened bottle under Dr. Bird's nose. The doctor lay for a moment without movement, and then he coughed and sat up half strangled with tears running down his face.
"Take that confounded bottle away, Carnes!" he said. "Do you want to strangle me?"
He sat up and looked around.
"What happened?" he demanded. "Oh, yes, I remember now. That brute was about to operate on me. How did you get here?"
"Never mind that, Doctor. Are you all right?"
"Right as a trivet, old dear. How did you get here so opportunely?"
"I was a little slow in locating Lieutenant Maynard and the marines. When we got here I was afraid that we couldn't find the door, so I took Maynard and a detail around to the back and I went up to the top and slid down our cord and looked in the window. You were unconscious and Slavatsky was bending over you with a needle in his hand. I was about to try a shot at him when something called their attention to the men in front and I squeezed through the window and dropped in on them. They didn't seem any too glad to see me, but I overlooked that and insisted on inviting the rest of my friends in to share in the party. That's all."
"Carnes," said the Doctor, "you're probably lying like a trooper when you make out that you did nothing, but I'll pry the truth out of you sooner or later. Now I've got to get to work. Send for Lieutenant Maynard."
One of the marines went out to get the flyer, and Dr. Bird stepped to the cabinet from which Slavatsky had taken his record book earlier in the evening and took out the leather-bound volume. He opened it and had started to read when Lieutenant Maynard entered the cave.
"Hello, Maynard," said the Doctor, looking up. "Are the rest of the party on their way?"
"They will be here in less than two hours, Doctor."
"Good enough! Have some one sent to guide them here. In the meanwhile, I'm going to study these records. Keep the prisoners quiet. If they make a noise, gag them. I want to concentrate."
For an hour and a half silence reigned in the cave. A stir was heard outside and Admiral Clay, the President's personal physician, entered leading a stout gray-haired man. Dr. Bird whistled when he saw them and leaped to his feet as another figure followed the admiral.
"The President!" gasped Carnes as the officers came to a salute and the marines presented arms.
The President nodded to his ex-guard, acknowledged the salute of the rest and turned to Dr. Bird.
"Have you met with success, Doctor?" he asked.
"I have, Mr. President; or, rather, I hope that I have. At the same time, I would rather experiment on some other victim of their deviltry than the one you have brought me."
"My decision that the one I have brought shall be the first to be experimented on, as you term it, is unalterable."
Dr. Bird bowed and turned to the dwarf who had been a sullen witness of what had gone on.
"Slavatsky," he said slowly, "your game is up. I have witnessed one of your brain transfusions and I know the method. I gather from your notes that the menthium you have hidden in that cabinet is still as potent as when it was first extracted from a living brain, but in this case I am going to draw it fresh from one of your gang. Some of the details of the operation are a little hazy to me, but those you will teach me. I am going to restore this man to the condition he was in before you did your devil's work on him and you will direct my movements. Just what is the first step in removing the menthium from a brain?"
The dwarf maintained a stubborn silence.
"You refuse to answer?" asked the Doctor in feigned surprise. "I thought that you would rather instruct me and have me try the operation first on other men. Since you prefer that I operate on you first, I will be glad to do so."
He stepped to the opposite wall and in a few moments had opened the dwarf's hiding place and taken