So that’s the “Port of Missing Planes,” mused Dick Purdy as he looked down over the side of his cockpit. “It looks wild and desolate all right, but at that I can’t fancy a bus cracking up here and not being found pronto. Gosh, Wilder cracked in the wildest part of Arizona and he was found in a week.”

The mail plane droned monotonously on through perfect flying weather. Purdy continued to study the ground. Recently transferred from a western run, he was getting his first glimpse of that section of ill repute. Below him stretched a desolate, almost uninhabited stretch of country. By looking back he could see Bellefonte a few miles behind him, but Philipsburg, the next spot marked on his map, was not yet visible. Twelve hundred feet below him ran a silver line of water which his map told him was Little Moshannon Run. As he watched he suddenly realized that the ground was not slipping by under him as rapidly as it should. He glanced at his air-speed meter.

“What the dickens?” he cried in surprise. For an hour his speed had remained almost constant at one hundred miles an hour. Without apparent cause it had dropped to forty, less than flying speed. He realized that he was falling. A glance at his altimeter confirmed the impression. The needle had dropped four hundred feet and was slowly moving toward sea-level.

With an exclamation of alarm, Purdy advanced his throttle until the three motors of his plane roared at full capacity. For a moment his air-speed picked up, but the gain was only momentary. As he watched, the meter dropped to zero, although the propellers still whirled at top speed. His altimeter showed that he was gradually losing elevation.

He stood up and looked over the side of his plane. The ground below him was stationary as far as forward progress was concerned, but it was slowly rising to meet him. He fumbled at the release ring of his parachute but another glance at the ground made him hesitate. It was not more than three hundred feet below him.

“I must be dreaming!” he cried. The ground was no longer stationary. For some unexplained reason he was going backward. The motors were still roaring at top speed. Purdy dropped back into his seat in the cockpit. With his ailerons set for maximum lift he coaxed every possible revolution from his laboring motors. For several minutes he strained at the controls before he cast a quick glance over the side. His backward speed had accelerated and the ground was less than fifty feet below him. It was too close for a parachute jump.

“As slow as I’m falling, I won’t crack much, anyway,” he consoled himself. He reached for his switch and the roar of the motors died away in silence. The plane gave a sickening lurch backwards and down for an instant. Purdy again leaned over the side. He was no longer going either forward or back but was sinking slowly down. He looked at the ground directly under him. A cry of horror came from his lips. He sat back mopping his brow. Another glance over the side brought an expression of terror to his white face and he reached for the heavy automatic pistol which hung by the side of the control seat.

“He cleared Bellefonte at nine in the morning, Dr. Bird” said Inspector Dolan of the Post Office Department, “and headed toward Philipsburg. He never arrived. By ten we were alarmed and by eleven we had planes out searching for him. They reported nothing. He must have come to grief within a rather restricted area, so we sent search parties out at once. That was two weeks ago yesterday. No trace of either him or his plane has been found.”

“The flying conditions were good?”

“Perfect. Also, Purdy is above suspicion. He has been flying the mail on the western runs for three years. This is his first accident. He was carrying nothing of unusual value.”

“Are there any local conditions unfavorable to flying?”

“None at all. It is much uninhabited country, but there is no reason why it shouldn’t be safe country to fly over.”

“There are some damnably unfavorable local conditions, Doctor, although I can’t tell you what they are,” broke in Operative Carnes of the United States Secret Service. “Dick Purdy was rather more than an acquaintance of mine. After he was lost I looked into the record of that section a little. It is known among aviators as ‘The Port of Missing Planes.’”

“How did it get a name like that?”

“From the number of unexplained and unexplainable accidents that happen right there. Dugan of the air mail, was lost there last May. They found the mailbags where he had dropped them before he crashed, but they never found a trace of him or his plane.”

“They didn’t?”

“Not a trace. The same thing happened when Mayfield cracked in August. He made a jump and broke his neck in landing. He was found all right, but his ship wasn’t. Trierson of the army, dropped there and his plane was never found. Neither was he. He was seen to go down in a forced landing. He was flying last in a formation. As soon as he went down the other ships turned back and circled over the ground where he should have fallen. They saw nothing. Search parties found no trace of either him or his ship. Those are the best known cases, but I have heard rumors of several private ships which have gone down in that district and have never been seen or heard of since.”

Dr. Bird sat forward with a glitter in his piercing black eyes. Carnes gave a grunt of satisfaction. He knew the meaning of that glitter. The Doctor’s interest had been fully aroused.

“Inspector Dolan,” said Dr. Bird sharply, “why didn’t you tell me those things?”

“Well, Doctor, we don’t like to talk about mail wrecks any more than we have to. Of course, the loss of so many planes in one area is merely a coincidence. Probably the wrecked planes were stolen as souvenirs. Such things happen, you know.”

“Fiddlesticks!” said Dr. Bird sharply. He raised one long slender hand with beautifully modeled tapering fingers and threw back his unruly mop of black hair. His square, almost rugged jaw, protruded and the glitter in his eyes grew in intensity. “No souvenir hunting vandals could cart away whole planes without leaving a trace. In that case, what became of the bodies? No, Inspector, this has gone beyond the range of coincidence. There is some mystery here and it needs looking into. Fortunately, my work at the Bureau of Standards is in such shape that I can safely leave it. I intend to devote my entire time to clearing this matter up. The ramifications may run deeper than either you or I suspect. Please have all of your records dealing with plane disappearances or wrecks in that locality sent to my office at once.”

The Post Office inspector stiffened.

“Of course, Dr. Bird,” he said formally, “we are very glad to hear any suggestion that you may care to offer. When it comes, however, to a matter of surrendering control of a Post Office matter to the Department of Commerce or to the Treasury Department, I doubt the propriety. Our records are confidential ones and are not open to everyone who is curious. I will inform the proper authorities of your desire to help, but I doubt seriously if they will avail themselves of your offer.”

Dr. Bird’s black eyes shot fire. “Idiot!” he said. “If you’re a specimen of the Post Office Department, I’ll have the entire case taken out of your hands. Do you mean to cooperate with me or not?”

“I fail to see what interest the Bureau of Standards can have in the affair.”

“The Bureau isn’t mixed up in it; Dr. Bird is. If necessary, I will go direct to the President. Oh, thunder! What’s the use of talking to you? Who’s your chief?”

“Chief Inspector Watkins is in charge of all investigations.”

“Carnes, get him on the telephone. Tell him we are taking charge of the investigation. If he balks, have Bolton go over his head. Then get the chief of the Air Corps on the wire and arrange for an army plane to-morrow. There is something more than a mail robbery back of this or I’m badly fooled.”

“Do you suspect--”

“I suspect nothing and no one, Carnes--yet! I’ll get a few instruments together to take with us to-morrow. We’ll fly over that section until something happens if it takes us until this time next year.”

A three-seated scout plane rose from Langley Field at eight the next morning. Captain Garland was at the controls. In the rear cockpit sat Dr. Bird and Carnes. Inside his flying helmet, the doctor wore a pair of headphones which were connected to a box on the floor before him. Carnes carried no apparatus but his hand rested carelessly on the grip of a machine-gun.

The plane cleared Bellefonte at nine-thirty and bore east toward Philipsburg. Captain Garland kept his eyes on his instrument board and on a map. Less than six hundred feet above the ground, he was following the air-mail route as exactly as possible. Overhead a mail plane winged its way east, three thousand feet above them.

Fifteen minutes brought them to Philipsburg. Captain Garland shot his plane upward a few hundred feet.

“Turn back, Captain,” said Dr. Bird into the speaking tube. “Retrace your course a quarter of a mile farther north. At Bellefonte, turn back and go over the same ground another quarter of a mile north. Keep flying back and forth, working your way north, until I tell you to stop.”

The plane swung around and headed back toward Bellefonte.

“Of course, we can’t tell exactly what route he followed,” said the doctor to Carnes, “but he was new on this run and it is safe to assume that he didn’t stray far. We’ll quarter the whole area before we stop.”

Carnes watched the ground below them carefully. There was nothing about it to distinguish it from any other wooded mountainous country and his interest waned. He glanced aloft. The mail plane had disappeared in the distance and the sky was clear of aircraft. He turned again to the ground. It looked closer than it had before. He turned and looked at the duplicate altimeter. The plane had lost nearly a hundred feet elevation.

“There’s something wrong about this plane, Doctor,” came Captain Garland’s voice through the speaking tube. “It doesn’t behave like it should.”

“I guess we’ve found what we were looking for, Carnes,” said Dr. Bird grimly. “What seems to be the matter, Captain?”

“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 muffled accents from the front cockpit.

“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 cockpit 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 cock 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. Carnes reached toward the table for his light. Before he could reach it he was frozen into immobility. From the corner of his eye he could watch the doctor. Dr. Bird was struggling to bring the light back on the moles which stood before them. Great beads of sweat stood out on his forehead. Inch by inch he moved the light closer to his goal, but Carnes could see that his thumb was stealing up toward the switch button. His breath came in sobs. Suddenly the light went out.

For some time the two men sat motionless on the bench unable to speak or move. One of the moles stepped before them and gave a mental command. The two rose to their feet. For a mile or more they followed their guide, then, at a silent command, they turned to the right for a few steps and stopped. In another moment, the numbing influence had departed.

“Are you all right, Carnes?”

“Yes, right as can be. Doctor, what were those things? Where are we? What’s it all about?”

“We’ll find out in time, I guess,” replied the doctor with a chuckle. “Carnes, isn’t this the darnedest thing we’ve ever been through? Captured half a mile underground by a race of giant talpidae before whose mental orders we are as helpless as children. Did you understand any of their talk?”

“Talk? I didn’t hear any.”

“Well, mental conversation then. They made no sound.”

“No. All I understood was the orders I obeyed.”

“I got a great deal of it,” the doctor said. “We are evidently in or near a sort of central community of these fellows. They spoke; thought is a better word; they thought of doing away with us but decided to wait until they consulted someone with more authority. You see, we are not airplane pilots. Captain Garland was taken at once to the place where they have other aviators imprisoned.”

“What do they want of pilots underground?”

“I couldn’t quite get that. There was another thought that I am not sure that I interpreted correctly. If I did, there is some man of the upper world down here in a position of considerable authority among them. He has some use for pilots, but what use, I don’t know. We are to be held until he is consulted.”

“Who could it be?”

“I can only think of one man. Carnes, and I hope I’m wrong. I don’t have to name him.”

“You mean--?”

“Ivan Saranoff. We haven’t heard of him or had any activity from him for the last eight months. We know that he had a subterranean borer with which he has penetrated deep into the earth. Isn’t it possible that he has, at some time in his explorations, come into contact with these fellows and made friends with them?”

“It’s possible, Doctor, but I hoped we had killed him when we destroyed his borer.”

“So did I, but he seems to bear a charmed life. Several times we have thought him dead, only to have him show up with some new form of devil’s work. It is too much to hope that we have succeeded in doing away with him. Did you notice one thing? Those fellows were helpless while I held the light on them. The one which was holding us captive got so interested in the discussion about our fate that he momentarily forgot us. That was when I got my light. Until I turned the light away from them, we were free men.”

“That’s right,” answered the secret service man.

“Remember that. The next time we get a light on a bunch of them, hold them in the beam until we can make terms.”

“If we ever get hold of a light again.”

“I have a light they didn’t get, probably because I didn’t think of it while they were around. It is one of those fountain pen battery affairs and they probably took it for a pen. I won’t turn it on now, partly to save it and partly not to let them know we have it. Let’s see what our prison is like.”

They felt their way around the room. It proved to be eight paces by ten in size. Like the tunnels it was floored with crepe rubber or some similar substance which gave out no sound of footsteps, yet was firm underfoot. The room was furnished with two beds, a table and two chairs. There was no sign of a door.

“That’s that,” exclaimed the doctor when they had finished their exploration. “I’m hungry. I wonder when we eat. Hello, here comes one of the fellows now.”

Carnes made no reply. As the doctor’s speech ended, a wave of mental power enveloped the room. One of the moles entered, moved over to the table for an instant and then left the room. An earthly odor of vegetables pervaded the room.

“My question is answered,” said the doctor. “We eat now.”

He moved to the table. On it had been placed dishes containing three different types of roots. Two of them proved to be palatable, but the third was woody and bitter. The prisoners made a hearty meal from the two they relished. For an hour they sat waiting.

“Here they come again!” exclaimed the doctor. “We are going before the person I spoke of. Can’t you get their thoughts?”

“No, I can’t, Doctor. I can understand when I get a command, but aside from those times everything is a blank to me.”

“My mental wave receiver, if that’s what it is, must be attuned to a different frequency than yours, for I can hear them talking to one another. I guess I should say that I can feel them thinking to one another. At any rate, they want us to follow. Come along, the road will be open and level.”

The doctor stepped out confidently with Carnes at his heels. For half a mile they went forward. Presently they halted.

“We are in a big chamber here, Carnes,” whispered the doctor, “and there is someone before us. We’ll have some light in a minute.”

His prophecy was soon fulfilled. A vague glimmer of light began to fill the cavern in which they stood. As it grew stronger they could see a raised dais before them on which were seated three figures. Two of them were the giant moles. Each of the moles wore a helmet which covered his head completely, with no sign of lenses or other means of vision. It was the central figure, however, which held the attention of the prisoners.

Seated on a chair and regarding, them with an expression of sardonic amusement was a man. Above a high forehead rose a thin scrub of white hair. Keen brown eyes peered at them from under almost hairless brows. The nose was high bridged and aquiline and went well with his prominent cheekbones. His mouth was a mere gash below his nose, framed by thin bloodless lips. The lips were curled in a sneer, revealing yellow teeth. The whole expression of the face was one of revolting cruelty.

“So,” said the figure slowly, “fate has been kind to me. My friends, Dr. Bird and Operative Carnes have chosen to pay me a long visit. I am greatly flattered.”

The thin metallic voice with its noticeable accent struck a familiar chord.

“Saranoff!” gasped Carnes.

“Yes, Mr. Carnes, Saranoff. Professor Ivan Saranoff, of the faculty of St. Petersburg once. Now merely Saranoff, the scourge of the bourgeois.”

“I hoped we had killed you,” murmured Carnes.

“It was no fault of Dr. Bird’s that he failed,” replied the Russian with an excess of malevolence in his voice. “His method was a correct one. Merely the fortuitous fact that we had just pierced one of the tunnels of the Selom, and I was away from my borer exploring it, saved me. You did me a good turn, Doctor, without meaning to. You destroyed an instrument on which I had relied. In doing so, you unwittingly delivered into my hands a power greater than any I had dreamed of--the Selom.”

“What can a mental cripple like you do with blind allies like them?” asked Dr. Bird with a contemptuous laugh. The Russian half rose from his seat in rage. For a moment his hand toyed with a switch before him. The sardonic sneer came back into his face and he dropped back into his seat.

“You nearly provoked me to destroy you, Doctor,” he said, “but cold calculation saved you. Since you will never return to the upper world, save when and as I decree, I have no objection to telling you. The Selom are not blind. Their eyes are under the skin as is the case with many of the talpidae, but for all that they can see very well. Their eyes function on a shorter wave than ours, a wave so short that it readily penetrates through miles of earth and rock. This cavern is now flooded with it. Visible light, the light by which we see, is limited to their eyes, hence the helmets which you see. They can see through those helmets as well as you or I can see through air.”

“What do you intend to do with us?”

“Ah, Doctor, there you hit me in a tender spot. I have a sore temptation to close this switch on which my hand rests. Were I to do so, both you and Mr. Carnes would vanish forevermore. I have, however, conceived a very real affection for you two. Your brains, Doctor, working in my behalf instead of against me would render me well-nigh omnipotent. Mr. Carnes has a certain low cunning which I can also use to advantage. Both of you will join me.”

“You might as well close your switch and save your breath, Saranoff, for we will do nothing of the sort,” replied the doctor sharply.

“Ah, but you will. So will Mr. Carnes. I had no hopes that you would join me willingly. In fact, I am pleased that you do not. I could never trust you. All the same, you will join my forces as have the others whom I have brought into the hands of the Selom. I have ways of accomplishing my desires. It pleases my fancy, Doctor, to use your brains in aiding me in my scientific developments. You will enjoy working with the scientists of the Selom. Among them you will find brains which excel any to be found on the surface of the earth, since we two are below. Already I have learned much from them. You, Mr. Carnes shall be taught to pilot an airplane. When my cohorts go forth from the realms of the Selom to establish the rule of Russia, you will be piloting one of the planes. Your first task will be to learn to fly.”

“I refuse to do anything of the sort!” said Carnes.

“I will not be ready to have your flying lessons started until to-morrow,” replied the Russian, “and you will have until then to reconsider your rash decision. It will be much easier for you if you obey my orders. If you still refuse to-morrow, you will pay a visit to the laboratory of the Selom. When you return your lessons will be started. You will now be taken to your cell. I have use for Dr. Bird this afternoon.”

“I won’t leave Dr. Bird and that’s flat!” exclaimed Carnes. Dr. Bird interrupted him.

“Go ahead, Carnesy, old dear,” he said lightly. “You might just as well toddle along under your own power as to be dragged along. You have a day for reflection, in any event. I daresay I’ll see you again before they do anything to you.”

Carnes glanced keenly at the doctor’s face. What he saw evidently reassured him for he turned without a word and walked away. The light grew gradually dimmer until darkness again reigned in the cavern.

“Come, Doctor,” said Saranoff’s voice. “We have work to do.”

Carnes sat alone in his cell for hours. The darkness and loneliness wore on him until he felt that his nerves would crack. Not a sound came to him. He threw himself on one of the beds and plugged his ears with his finger tips in an attempt to keep the silence out. Then a cheerful voice sounded in the cell and a friendly hand fell on his shoulder.

“Well, Carnesy, old dear,” said Dr. Bird, “have you been lonesome?”