"Blessed if I know," was the answer. "It feels like a drag of some sort, like an automobile going through heavy sand. We're slowing down, though I am giving her all the gun I've got!"

"Cut your motor!" said the doctor shortly. He bent over the duplicate instrument board as the roar of the motor died away. Carnes rose and looked over the side.

"Look, Doctor!" he cried in a strained voice. Directly below them yawned a hole sixty feet in diameter and extending down into the bowels of the earth. The plane hovered over the hole for a moment and then slowly descended into it.

"What is it?" cried the detective.

"It's the secret of the Port of Missing Planes," replied Dr. Bird.

"Throw off your parachute. Keep your gun and light handy but don't fire unless I do first. The same holds good for you, Captain."

The plane sunk until it was fifty feet below the level of the ground.

Carnes looked up. Gradually the circle of sky became blurred and hazy as though the air were heavy with dust. The rasp of Dr. Bird's flashlight key aroused him and he hastily wound his own. The haze above them grew thicker. Suddenly the light died and then came darkness, a darkness so thick and absolute that it bore down on them like a weight. Dr. Bird's light stabbed a path through it.

They were in a tunnel or tube reaching into the ground. The sides were smooth and polished, as though water worn. The plane sank deeper and deeper into the earth. Suddenly Dr. Bird's light went out.

"What's the matter, Doctor?" asked Carnes, "did your light fail?"

"No," came a strained voice. "I turned it out."

"Why?"

"I don't know. Light yours."

Carnes reached into his pocket. Dr. Bird could hear his breath come in panting sobs as though he were exerting his whole strength.

"I can't do it, Doctor," he gasped. "I want to, but some power greater than my will prevents me."

"Are you affected, Captain?" asked the Doctor.

"I--can't--move," came in m.u.f.fled accents from the front c.o.c.kpit.

"Some power beyond my knowledge has us in its grasp," said the doctor.

"All we can do is sit tight and see what happens. We are no longer falling at any rate."

From the forward c.o.c.kpit came a rustling sound. There was a slight jar in the ship, and it gave as though a weight had been applied to one side.

"What are you doing, Garland?" asked the doctor sharply.

There was no reply. Again came the rustling sound. The ship gave a sudden lurch as though a weight had left the side. Carnes suddenly spoke.

"Good-by, Doctor," he said. "I'm going over the side."

"I have been fighting it but I'm going myself in a minute," replied the doctor grimly. "Something is pulling me over. It's the same power that keeps me from turning on my light."

"It's perfectly safe to go over," said Carnes suddenly. "The plane is resting on a solid base."

"I have the same feeling. Catch hold of my belt and let's go."

They climbed over the side of the plane and dropped to the ground.

Their descent made absolutely no sound. Dr. Bird stopped and felt the floor.

"Crepe rubber, or something of the sort," he murmured. "At any rate, it's noise and vibration proof."

"Now what?" asked Carnes.

"This way," replied the doctor confidently. "I'm beginning to get the hang of understanding this. The way is perfectly level and open before us. Keep your hand on my shoulder and step right out."

"How do you know where we're going?"

"I don't, but something tells me that the road is level and open. It is the same thing that brought us over the side. I can't explain it but it is some sort of a telepathic control exerted by an intelligence. Whether the sending mind is reinforced by instruments I don't know, but I rather fancy not."

"Where is Garland?"

"He went off in another direction. I could feel the power that guided him although it was not directed at us. Something tells me that he is safe for the present."

For half a mile they made their way through the darkness before they stopped. This time Carnes could plainly understand the command which came to both of them.

"There is a table before us," said Dr. Bird. "Lay your flashlight and pistol on it."

Carnes struggled against the order but the power guiding him was stronger than his will. He strove to turn on his light. When he could not, he tried to c.o.c.k his pistol. With a sigh, he laid his gun and light on the table before him. Without words, the two men walked forward a few feet and sat confidently down on a bench that something told them was there.

For a moment they sat quietly. A cry, choked in the middle, came from the detective's throat. Cold clammy hands touched his face. He strove again to cry out, but his voice was paralyzed. The hands went methodically over his body, evidently searching for weapons. Mustering up his will, Carnes made a grab for one of them. His captor apparently had no objection to the detective's action for Carnes seized the hand without effort. But he almost dropped it. The hand was as large as a ham. He reached for the other hand but could not locate it. A movement on the part of his captor brought it to him and he made the startling discovery that the palms were directed outward. The hand had only four fingers, which were armed with long curved claws instead of nails.

Carnes ran his hand up the palm to search for a thumb but found none.

He found, however, that, while the hands were naked, the wrists were covered with short thick fur.

"Doctor!" he cried, "there's--"

Again came the overpowering will and his speech died away in silence.

He sat dumb and motionless while his captor moved over to Dr. Bird. A second animal came forward and felt the detective over. He was not allowed to move this time, nor was he while a third and fourth animal went carefully over him. The four drew back some distance.

"Doctor," whispered Carnes as the influence grew fainter.

"Shh!" was the answer, and as the doctor's demand for silence was reinforced by another wave of the paralyzing power, Carnes had no choice. As he sat there silent, the power which held him again seemed to grow less. He found that he could move his arms slightly. He edged forward to get his gun and light. Before he reached them, a beam of light split the darkness. Dr. Bird stood, electric torch in hand, staring before him.

At a distance of a few feet stood a group of half a dozen animals about the height of a man as they stood erect on their short hind legs. They were covered with heavy brown fur. Their lower limbs were thin and light, but their shoulders and forelegs were heavy and powerful. Their forepaws, which had the palms facing outward, were armed with the long wicked claws he had felt. No visible ears protruded from the round skulls. Their heads appeared to rest between their shoulders, so short were their necks. Their muzzles were long and obtusely pointed. Through grinning jaws could be seen powerful white teeth.

"Talpidae!" cried Dr. Bird. "Carnes, they are a race of giant intellectual moles!"

Despite the fact that they had no visible eyes, the creatures were strongly affected by the light. They dropped on all fours and turned their backs to the scientist and the detective. Two of them scurried away down a long tunnel which opened from the room in which they stood. Dr. Bird turned his light up and swept the room. It was roughly circular, a hundred feet in diameter, with a roof ten feet high. Dozens of tunnels led off in every direction.

"Your light, Carnes, quick!" cried the doctor in a strained voice.