In a secluded spot among the hills of northern New Jersey stood the old DeBost mansion, a rambling frame structure of many wings and gables that was well-nigh hidden from the road by the half-mile or more of second-growth timber which intervened. High on the hill it stood, and it was only by virtue of its altitude that an occasional glimpse might be obtained of weatherbeaten gable or partly tumbled-down chimney. The place was reputed to be haunted since the death of old DeBost, some seven years previously, and the path which had once been a winding driveway was now seldom trod by human foot.

It was now two years since Edwin Leland bought the estate for a song and took up his residence in the gloomy old house. And it had then been vacant for five years since DeBost shot himself in the northeast bedroom. Leland’s associates were sure he would repent of his bargain in a very short time, but he stayed on and on in the place, with no company save that of his man-servant, an aged hunch-back who was known to outsiders only as Thomas.

Leland was a scientist of note before he buried himself in the DeBost place, and had been employed in the New York research laboratory of one of the large electrical manufacturers, where he was much admired and not a little envied by his fellow workers. These knew almost nothing of his habits or of his personal affairs, and were much surprised when he announced one day that he had come into a sizable fortune and was leaving the organization to go in for private research and study. Attempts to dissuade him were of no avail, and the purchase of the DeBost property followed, after which Leland dropped from sight for nearly two years.

Then, on a blustery winter day, a strange telephone call was received at the laboratory where he had previously worked. It was from old Thomas, out there in the DeBost mansion, and his quavering voice asked for Frank Rowley, the genial young engineer whose work had been most closely associated with Leland’s.

“Oh, Mr. Rowley,” wailed the old man, when Frank responded to the call, “I wish you would come out here right away. The master has been acting very queerly of late, and to-day he has locked himself in his laboratory and will not answer my knocks.”

“Why don’t you break in the door?” asked Frank, looking through the window at the snow storm that still raged.

“I thought of that, Mr. Rowley, but it is of oak and very thick. Besides, it is bound with steel or iron straps and is beyond my powers.”

“Why not call the police?” growled Frank. He did not relish the idea of a sixty or seventy mile drive in the blizzard.

“Oh--no--no--no!” Old Thomas was panicky at the suggestion. “The master told me he’d kill me if I ever did that.”

Before Frank could formulate a reply, there came a sharp gasp from the other end of the line, a wailing cry and a thud as of a falling body; then silence. All efforts to raise Leland’s number merely resulted in “busy” or “line out of order” reports.

Frank Rowley was genuinely concerned. Though he had never been a close friend of Leland’s, the two had worked on many a knotty problem together and were in daily contact during the nearly ten years that the other man had worked in the same laboratory.

“Say, Tommy,” said Frank, replacing the receiver and turning to his friend, Arnold Thompson, who sat at an adjoining desk, “something has happened out at Leland’s place in Sussex County. Want to take a drive out there with me?”

“What? On a day like this? Why not take the train?”

“Don’t be foolish, Tommy,” said Frank. “The place is eight miles from the nearest station, which is a flag stop out in the wilds. And, even if you could find a cab there--which you couldn’t--there isn’t a taxi driver in Jersey who’d take you up into those mountains on a day like this. No, we’ll have to drive. It’ll be okay. I’ve got chains on the rear and a heater in the old coupe, so it shouldn’t be so bad. What do you say?”

So Tommy, who usually followed wherever Frank led, was prevailed upon to make the trip. He had no particular feeling for Leland, but he sensed an adventure, and, in Frank’s company, he could ask for no more.

Frank was a careful driver, and three hours were required to make the sixty-mile journey. Consequently, it was late in the afternoon when they arrived at the old DeBost estate. It had stopped snowing, but the drifts were deep in spots, and Frank soon found that the car could not be driven through the winding path from the road to the house. So they left it half buried in a drift and proceeded on foot.

It was a laborious task they had undertaken, and, by the time they set foot on the dilapidated porch, even Frank, husky and athletic as was his build, was puffing and snorting from his exertions. Little Tommy, who tipped the scales at less than a hundred and twenty, could hardly speak. They both were wet to the waist and in none too good humor.

“Holy smoke!” gasped Tommy, stamping the clinging snow from his sodden trouser legs and shoes, “if it snows any more, how in Sam Hill are we going to get out of this place?”

“Rotten trip I let you in for Tommy,” growled Frank, “and I hope Leland’s worth it. But, darn it all, I just had to come.”

“It’s all right with me, Frank. And maybe it’ll be worth it yet. Look--the front door’s open.”

He pointed to the huge oaken door and Frank saw that it was ajar. The snow on the porch was not deep and they saw that footprints led from the open door to a corner of the porch. At that point the snow on the railing was disturbed, as if a hurrying man had clung to it a moment before jumping over and into the drifts below. But the tracks led no further, for the drifting snow had covered all excepting a hollow where some body had landed.

“Thomas!” exclaimed Frank. “And he was in a hustle, by the looks of the tracks. Bet he was frightened while at the telephone and beat it.”

They entered the house and closed the door behind them. It was growing quite dark and Frank searched for the light switch. This was near the door, and, at pressure on the upper button, the spacious old hall with its open staircase was revealed dimly by the single remaining bulb in a cluster set in the center of the high ceiling. The hall was unfurnished, excepting for a telephone table and chair, the chair having fallen to the floor and the receiver of the telephone dangling from the edge of the table by its cord.

“You must have heard the chair fall,” commented Tommy, “and it sure does look as if Thomas left in a hurry. Wonder what it was that frightened him?”

The house was eerily silent and the words echoed awesomely through the adjoining rooms which connected with the hall through large open doorways.

“Spooky place, isn’t it?” returned Frank.

And then they were both startled into immobility by a rumble that seemed to shake the foundations of the house. Heavier and heavier became this vibration, as if some large machine was coming up to speed. Louder and louder grew the rumble until it seemed that the rickety old house must be shaken down about their ears. Then there came a whistling scream from the depths of the earth--from far underground it seemed to be--and this mounted in pitch until their eardrums tingled. Then abruptly the sounds ceased, the vibration stopped, and once more there was the eery silence.

Rather white-faced, Tommy gazed at Frank.

“No wonder old Thomas beat it!” he said. “What on earth do you suppose that is?”

“Search me,” replied Frank. “But whatever it is, I’ll bet it has something to do with Leland’s strange actions. And we’re going to find out.”

He had with him the large flashlamp from the car, and, by its light, the two made their way from room to room searching for the iron-bound door mentioned by Thomas.

They found all rooms on the first and second floors dusty and unused with the exception of two bedrooms, the kitchen and pantry, and the library. It was a gloomy and spooky old house. Floor boards creaked startlingly and unexpectedly and the sound of their footsteps echoed dismally.

“Where in time is that laboratory of Leland’s?” exclaimed Frank, his ruddy features showing impatient annoyance, exaggerated to an appearance of ferocity by the light of the flashlamp.

“How about the cellar?” suggested Tommy.

“Probably where it is,” agreed Frank, “but I don’t relish this job so much. I’d hate to find Leland stiff down there, if that’s where he is.”

“Me, too,” said Tommy. “But we’re here now, so let’s finish the job and get back home. It’s cold here, too.”

“You said it. No steam in the pipes at all. He must have let the fire go out in his furnace, and that’s probably in the cellar too--usually is.”

While talking, Frank had opened each of the four doors that opened from the kitchen, and the fourth revealed a stairway that led into the blackness beneath. With the beam of his torch directed at the steps, he proceeded to descend, and Tommy followed carefully. There was no light button at the head of the stairs, where it would have been placed in a more modern house, and it was not until they had reached the furnace room that they located a light fixture with a pull cord. An ordinary cellar, with furnace, coal bin, and a conglomeration of dust-covered trunks and discarded furniture, was revealed. And, at its far end, was the iron-bound door.

The door was locked and could not be shaken by the combined efforts of the two men.

“Have to have a battering ram,” grunted Frank, casting about for a suitable implement.

“Here you are,” called Tommy, after a moment’s search. “Just the thing we are looking for.”

He had come upon a pile of logs, and one of these, evidently a section of an old telephone pole, was of some ten or twelve inches diameter and about fifteen feet long. Frank pounced upon it eagerly, and, supporting most of the weight himself, led the attack on the heavy oak door with the iron bands.

No sound from within greeted the thunderous poundings. Clearly, if Leland was behind that door, he was either dead or unconscious.

Finally the double lock gave way and Tommy and Frank were precipitated headlong into the brightly lighted room beyond. Recovering their balance, they took stock of their surroundings and were amazed at what they saw--a huge laboratory, fitted out with every modern appliance that money could buy. A completely equipped machine shop there was; bench after bench covered with the familiar paraphernalia of the chemical and physical laboratory; huge retorts and stills; complicated electrical equipments; dozens of cabinets holding crucibles, flasks, bottles, glass tubing, and what not.

“Good Lord!” gasped Tommy. “Here’s a laboratory to more than match our own. Why, Leland’s got a fortune invested here!”

“I should say so. And a lot of stuff that our company does not even have. Some of it I don’t know even the use of. But where is Leland?”

There was no sign of the man they had come to help. He was not in the laboratory, though the door had been locked from within and the lights left burning throughout.

With painstaking care they searched every nook and cranny of the large single room and were about to give up in despair when Tommy happened to observe an ivory button set into the wall at the only point in the room where there were no machines or benches at hand. Experimentally he pressed the button, and, at the answering rumble from under his feet, jumped back in alarm. Slowly there opened in the paneled oak wall a rectangular door, a door of large enough size to admit a man. From the recess beyond there came a breath of air, foul with the musty odor of decayed vegetation, dank as the air of a tomb.

“Ah-h-h!” breathed Frank. “So that is where Ed Leland is hiding! The secret retreat of the gloomy scientist!”

He spoke half jestingly, yet when he squeezed his stalwart bulk through the opening and flashed the beam of his light into the darkness of a narrow passage ahead he was assailed with vague forebodings. Tommy followed close behind and spoke not a word.

The passage floor was thick with dust, but the marks of many footsteps going and returning gave mute evidence of the frequency of Leland’s visits. The air was heavy and oppressive and the temperature and humidity increased as they progressed along the winding length of the rock-walled passageway. The floor sloped, ever downward and, in spots, was slippery with slimy seepage. It seemed that they turned back on their course on several occasions but were descending deeper and deeper into the heart of the mountain. Then, abruptly, the passage ended at the mouth of a shaft, which dropped vertically from almost beneath their feet.

“Whew!” exclaimed Frank. “Another step and I’d have dropped into it. That’s probably what happened to Leland.”

He knelt at the rim of the circular opening and looked into the depths of the pit, Tommy following suit. The feeble ray of the flashlight was lost in the blackness below.

“Say, Frank,” whispered Tommy, “turn off the flash. I think I saw a light down there.”

And, with the snapping of the catch, there came darkness. But, miles below them, it seemed, there was a tiny pin-point of brilliance--an eery green light that was like a wavering phosphorescence of will-o’-the-wisp. For a moment it shone and was gone. Then came the dreadful vibration they had experienced in the hall of the house--the whistling scream that grew louder and louder until it seemed they must be deafened. The penetrating wail rose from the depths of the pit, and the vibration was all around them, in the damp rock floor on which they knelt, and in the very air of the cavern. Hastily Frank snapped on the light of his flash.

“Oh boy!” he whispered. “Leland is certainly up to something down there and no mistake! How’re we going to get down?”

“Get down?” asked Tommy. “You don’t want to go down there, do you?”

“Sure thing. We’re this far now and, by George, we’re going to find out all there is to learn.”

“How deep do you suppose it is?”

“Pretty deep, Tommy. But we can get an idea by dropping a stone and counting the seconds until it strikes.”

He played the light of the flash over the floor and soon located a smooth round stone of the size of a baseball. This he tossed over the rim of the pit and awaited results.

“Good grief!” exclaimed Tommy. “It’s not falling!”

What he said was true, for the stone poised lightly over the opening and drifted like a feather. Then slowly it moved, settling gradually into oblivion. Frank turned the flash downward and they watched in astonishment as the two-pound pebble floated deliberately down the center of the shaft at the rate of not more than one foot in each second.

“Well, I’ll be doggoned,” breathed Frank admiringly. “Leland has done it. He has conquered gravity. For, in that pit at least, there is no gravity, or at any rate not enough to mention. It has been almost completely counteracted by some force he has discovered and now we know how to follow him down there. Come on Tommy, let’s go!”

And, suiting action to his words, Frank jumped into the mouth of the pit where he bobbed about for a moment as if he had jumped into a pool of water. Then slowly he sank from view, and Tommy followed him.

It was a most unique experience, that drop into the heart of the mountain. Practically weightless, the two young men found it quite difficult to negotiate the passage. For the first hundred or more feet they continued to bump about in the narrow shaft and each sustained painful bruises before he learned that the best and simplest method of accommodating himself to the strange condition was to remain absolutely motionless and allow the greatly weakened gravity to take its course. Each movement of an arm or leg was accompanied by a change in direction of movement, and contact with the hard stone walls followed. If they endeavored to push themselves from the contact the result was likely to be an even more serious bump on the opposite side of the shaft. So they continued the leisurely drop into the unknown depth of the pit.

Frank had turned off the flashlamp, for its battery was giving out and he wished to conserve its remaining energy for eventualities. Thus they were in Stygian darkness for nearly a half-hour, though the green luminosity far beneath them grew stronger with each passing minute. It now revealed itself as a clearly defined disc of light that flickered and sputtered continually, frequently lighting the lower end of the shaft with an unusual burst of brilliance. Remotely distant it seemed though, and unconscionably slow in drawing nearer.

“How far do you think we must drop?” called Tommy to Frank, who was probably fifty feet below him in the shaft.

“Well, I figure we have fallen about a thousand feet so far,” came the reply, “and my guess is that we are about one third of the way down.”

“Then this shaft is over a half-mile deep, you think?”

“Yes, at least a thousand yards, I should say. And I hope his gravity neutralizing machinery doesn’t quit all of a sudden and let us down.”

“Me, too,” called Tommy, who had not thought of that possibility.

This was no joke, this falling into an unknown region so far beneath the surface of good old mother earth, thought Tommy. And how they would ever return was another thing that was not so funny. Frank was always rushing into things like this without counting the possible cost and--well--this might be the last time.

Gradually the mysterious light became stronger and soon they could make out the conformation of the rock walls they were passing at such a snail’s pace. Layers of vari-colored rock showed here and there, and, at one point there was a stratum of gold-bearing or mica-filled rock that glistened with a million reflections and re-reflections. The air grew warmer and more humid as they neared the mysterious light source. They moved steadily, without acceleration, and Frank estimated the rate at about forty feet a minute. Then, with blinding suddenness, the light was immediately below and they drifted into a tremendous cavern that was illuminated by its glow.

Directly beneath the lower end of the shaft through which they had passed, there was a glowing disc of metal about fifteen feet in diameter. They drifted to its surface and sprawled awkwardly where they fell. Scrambling to gain a footing, they bounced and floated about like toy balloons before realizing that it would be necessary to creep slowly from the influence of that repelling force which had made the long drop possible without injury. Gravity met them at the disc’s edge with what seemed to be unusual violence.

At first it seemed that their bodies weighed twice the normal amount, but this feeling soon passed and they looked about them with incredulous amazement. The metal disc was quite evidently the medium through which the repelling force was set up in the shaft, and to this disc was connected a series of heavy cables that led to a pedestal nearby. On the pedestal was a controlling lever and this moved over a quadrant that was graduated in degrees, one end of the quadrant being labeled “Up” and the other “Down.” The lever now stood at a point but a very few degrees from the center or “Zero” mark and on the down side. Frank pulled this lever over to the full “Down” position and they found that they could walk over the disc with normal gravity.

“I suppose,” said Frank, “that if the lever is at the other end of the scale one would fall upward with full gravity acceleration--reversed. At zero, gravity is exactly neutralized, and the intermediate positions are useful in conveying materials or human beings up and down the shaft as desired. Very clever; but what is the reason for it all?”

In the precise center of the great cavern there was a dome or hemisphere of polished metal, and it was from this dome that the eery light emanated. At times, when the light died down, this dome gleamed with dull flickerings that threatened to vanish entirely. Then suddenly it would resume full brilliance, and the sight was marvelous beyond description. A slight hissing sound came from the direction of the dome, and this varied in intensity as did the light.

“Gosh!” said Tommy. “That looks like silver to me. And, if it is, what a wealthy man our friend Leland has become. He has spent his fortune well, even if he used it all to get to this.”

“Yes, but where is he?” commented Frank. Then: “Leland! Leland!” he called.

His voice echoed through the huge vault and re-echoed hollowly. But there was no reply save renewed flickerings from the dome.

Leaving the vicinity of the gravity disc, the two men advanced in the direction of the shining dome, which was about a quarter-mile from where they stood. Both perspired freely, for the air was very close and the temperature high. But the light of the dome was as cold as the light of a firefly and they had no hesitancy in drawing near. It was a beautiful sight, this dome of silver with its flickering lights and perfect contour.

“By George, I believe it is silver,” exclaimed Frank, when they were within a few feet of the dome. “No other metal has that precise color. And look! There is a wheelbarrow and some mining tools. Leland has been cutting away some of the material.”

Sure enough, there was indisputable evidence of the truth of his statement. And the material was undoubtedly silver!

“Silver Dome,” breathed Tommy, holding a lump of the metal in his hand. “A solid dome of pure silver--fifty feet high and a hundred in diameter. How much does that figure in dollars and cents, Frank?”

“Maybe it isn’t solid,” said Frank dryly, “though it’s worth a sizeable fortune even if it is hollow. And we haven’t found Leland.”

They circled the dome twice and looked into every corner of the great cavern, but there was no sign of the man for whom they searched. The wheelbarrow was half filled with lumps of the heavy metal, and maul and drill lay where they had been dropped by the lone miner. A cavity three feet across, and as many deep, appeared in the side of the dome to show that considerably more than one wheelbarrow load had been removed.

“Funny,” grunted Tommy. “Seems almost like the old dome had swallowed him up.”

At his words there came the terrific vibration. The light of the dome died out, leaving them in utter darkness, and from its interior there rose the mounting scream that had frightened old Thomas away. From so close by it was hideous, devastating; and the two men clung to each other in fright, expecting momentarily that the earth would give way beneath their feet and precipitate them into some terrible depth from which there could be no return.

Then the sound abruptly ceased and a gleam of light came from under the dome of silver. A crack appeared between its lower edge and the rocky floor of the cavern, and through this crack there shone a light of dazzling brilliancy--a warm light of rosy hue. Wider grew the opening until there was a full three feet between the floor and the bottom of the dome. Impelled by some irresistible force from within, the two men stumbled blindly to the opening, fell to the floor and rolled inside.

There was a heavy thud and the dome had returned to its normal position, with Frank and Tommy prisoners within its spacious hollow. The warm light bathed them with fearful intensity for a moment, then faded to a rosy glow that dulled their senses and quieted their nerves. Morpheus claimed them.

When Frank awoke he found himself between silken covers, and for a moment he gazed thoughtfully at a high arched ceiling that was entirely unfamiliar. Then, remembering, he sprang from the downy bed to his feet. The room, the furnishings, his silken robe, everything was strange. His bed, he saw, was a high one, and the frame was of the same gleaming silver as the dome under which they had been trapped. The arched ceiling glowed softly with the same rosy hue as had the inner surface of the dome. A large pool of water invited him, the surface of the pool being no more than a foot below the point where it was built into the tile floor of the room. A large open doorway connected with a similar adjoining room, where he suspected Tommy had been taken. On his bare toes, he moved silently to the other room and saw that his guess had been correct. Tommy lay sleeping quietly beneath covers as soft as his own and amidst equal luxury of surroundings.

“Well,” he whispered, “this doesn’t look as though we would come to any harm. And I might as well take a dive in that pool.”

Returning to his own room, he removed the silken garment with which he had been provided and was quietly immersed in the cool, invigorating water of the bath. His head cleared instantly.

“Hi there!” called Tommy from the doorway. “Why didn’t you wake me up? Where are we, anyway?”

With dripping head and shoulders above the water, Frank was compelled to laugh at the sleepy-eyed, wondering expression on the blue-jowled face of his friend. “Thought you were dead to the world,” he returned, “you old sleepy-head. And I don’t know where we are, excepting that it is somewhere under the silver dome. What’s more, I don’t much care. You should get into this water. It’s great!”

So saying, he dived to the bottom of the pool and stood on his hands, his feet waving ludicrously above the surface. Tommy sniffed once and then made a quick dash for the pool in his own room. He was not to be outdone by his more energetic partner.

A half-hour later, shaved and attired in their own garments, which had been cleaned and pressed and hung neatly in the closets, they settled themselves for a discussion of the situation. Having tried the doors of both rooms and found them locked from the outside, there was no other course open to them. They must await developments.

“Looks like Leland has quite an establishment down here inside the mountain,” ventured Tommy.

“Hm!” snorted Frank, “this place is none of Leland’s work. He is probably a prisoner here, as are we. He just stumbled on to the silver dome and was captured by whatever race is living down here beneath it, the same as we were. Who the real inhabitants are, and what the purpose of all this is, remains to be seen.”

“You think we are in friendly hands?”

“These quarters do not look much like prison cells, Tommy, but I must admit that we are locked in. Anyhow, I’m not worrying, and we will soon learn our fate and have to be ready to meet it. The people who own this place must have everything they want, and they sure have some scientific knowledge that is not known to us on the surface.”

“Wonder if they are humans?”

“Certainly they are. You never heard of wild beasts sleeping in beds like these, did you?”

Tommy laughed at he examined the exquisite hand-wrought figures on the silver bedstead. “No, I didn’t,” he admitted; “but where on earth did they come from, and what are they doing here?”

“You ask too many questions,” replied Frank, shrugging his broad shoulders. “We must simply wait for the answers to reveal themselves.”

There was a soft rap at the door of Frank’s room, where the two men were talking.

“Come in,” called Frank, chuckling at the idea of such consideration from their captors.

A key rattled in the lock and the door swung open to admit the handsomest man they had ever set eyes on. He was taller than Frank by several inches, standing no less than six feet five in his thin-soled sandals, and he carried himself with the air for an emperor. His marble-white body was uncovered with the exception of a loin cloth of silver hue, and lithe muscles rippled beneath his smooth skin as he advanced to meet the prisoners. His head, surmounted by curly hair of ebon darkness, was large, and his forehead high. The features were classic and perfectly regular. The corners of his mouth drew upward in a benign smile.

“Greetings,” he said, in perfect English and in a soft voice, “to the domain of Theros. You need fear no harm from our people and will be returned to the upper world when the time comes. We hope to make your stay with us enjoyable and instructive, and that you will carry back kind memories of us. The morning meal awaits you now.”

So taken aback were the two young Americans that they stared foolishly agape for a space. Then a tinkling laugh from the tall stranger set them once more at ease.

“You will pardon us, I hope,” apologized Frank, “but this is all so unexpected and so unbelievable that your words struck me speechless. And I know that my friend was similarly affected--We place ourselves in your hands.”

The handsome giant nodded understanding. “No offense was taken,” he murmured, “since none was intended. And your feelings are not to be wondered at. You may call me Orrin.”

He turned toward the open door and signified that they were to follow him. They fell in at his side with alacrity, both suddenly realizing that they were very hungry.

They followed in silent wonderment as Orrin led the way to a broad balcony that overlooked a great underground city--a city lighted by the soft glow from some vast lighting system incorporated in its vaulted ceiling high overhead. The balcony was many levels above the streets, which were alive with active beings of similar appearance to Orrin, these speeding hither and yon by means of the many lanes of traveling ways of which the streets were composed. The buildings--endless rows of them lining the orderly streets--were octagonal in shape and rose to the height of about twenty stories, as nearly as could be judged by earthly standards. There were no windows, but at about every fifth floor there was an outer silver-railed balcony similar to the one on which they walked. The air was filled with bowl-shaped flying ships that sped over the roof tops in endless procession and without visible means of support or propulsion. Yet the general effect of the busy scene was one of precise orderliness, unmarred by confusion or distracting noises.