The Rogan leader depressed another lever in the rock wall. The barred door slid slowly up, to reveal the receding darknesses of some great cave, or room, that adjoined the laboratory. Dex rolled his eyes so that he could watch the doorway; and, in a cold perspiration, waited for whatever might appear.

It was not long in coming!

The reptilian smell suddenly grew stronger. There was a booming hiss, a savage bellowing. A clattering of vast scales rattled out as some body weighing many tons was dragged over rock flooring. Then, before Dex's staring eyes appeared a huge, wedge-shaped head, at sight of which he bit his lips to keep from crying aloud.

Often enough he had seen one of those terrific heads looming in the fog of the northern hemisphere of Jupiter. He did not know the genus of the vast monster that bore it, but he did know it for the fiercest of the lizard giants that roamed the Jovian jungles. A creature larger than a terrestrial whale, with great long neck and heavy long tail dragging yards behind it, it would find the puny bulk of a man nothing but a morsel in its jaws!

Again the gigantic thing hissed and bellowed. And then its huge head came through the six-foot door and its neck uncoiled to send the gaping jaws within a foot of Dex. There it struggled to reach him, prevented by the small doorway that restrained the bulk of its enormous body, its head only inches away from the cleverly measured spot to which the metal rack had been wheeled.

Dex stared, hypnotized, into the dull, stony eyes of the beast, gasping for breath in the stench of its exhalations. The jaws snapped shut, fanning his cheek. He fought for self-control. Steady! Steady!

The slimy Rogans had no intention of feeding him to the thing yet. Not till they had made more determined efforts to wring from him the secret of the motor. They were just prefacing actual physical torture with h.e.l.lish mental torture, that was all.

That he was right in his guess was proved in a few moments. He heard a louder hiss from the great lizard so near him. Opening his eyes, he saw the Rogan leader in the process of forcing the serpentine neck to withdraw foot by foot back into the doorway, using his shock-tube as a sort of distant prod.

The monster swayed its ugly flat head back and forth, hissing deafeningly at the sting of the tube, now and again lunging with its vast unseen body at the too narrow entrance that kept it from entering the laboratory. Dex could hear the foundation walls of the building creak at the onslaught of that tremendous weight.

If it would only break through! he thought savagely. But it wasn't going to. In a short while it was cowed by the deadly tube, and withdrew its head awkwardly from the chamber. The barred door slid down into place: and the Rogan leader once more turned his attention to his prisoner.

"You will be wheeled within reach of the creature as the last step of your fate," Dex was informed. "Meanwhile, we shall start with something less deadly...."

A cogged wheel beside him was turning a notch. Dex felt the sliding bed of the rack crawl slightly under him. Intolerable tension was suddenly placed on his arms and legs. The leader stared at a spring dial; and moved the wheel another notch. The rack expanded again, stretching Dex's body till his joints cracked.

"You will tell us what we want to know," said the Rogan, glaring coldly down at him.

Dex compressed his lips stubbornly. He couldn't tell them if he wanted to, and, by G.o.d, he wouldn't if he could.

Another notch, the wheel was turned; and in spite of himself a groan escaped Dex's lips. One more notch, while the metal slide-rods beneath him lengthened a fraction of an inch....

CHAPTER VI

_The Inquisition_

Blind, animal fear caught Dex and shook him in its grip. Then rage filled his heart, driving out the fear as a gale dissipates fog. With pain-dimmed eyes he glared at the gangling, hateful figure that gazed down on him with icy eyes. If he could only blast that monstrous, physically feeble but mentally ferocious thing to bits! Annihilate it!

Blow it to the four corners of Jupiter! And all the other Rogans with it!

And with this thought he suddenly saw, through the red mists of rage, the shock-tube that was dangling indifferently from the Rogan leader's hand.

Instantly the red mists began to clear away. Another change took place in the tortured lieutenant's mind. The blind hot rage faded into more deadly, cold wrath. A plan began to bud into thought. It was a futile plan, really. It could not possibly accomplish anything vital. But it _might_ give him a chance for a little revenge before his life was snuffed out--might give him a chance to strike a blow for the dead Journeyman and the other gallant explorers who had perished here in this chamber before him.

He closed his eyes to hide the hate and calculation in them. The tall Rogan leaned lower over the rack.

"You are ready to do as I command?" he demanded.

"Yes," whispered Dex. "Yes."

In the beautiful Greca's eyes, as she translated his a.s.sent, was horror. But then, faintly, her mind caught the thought that lay beneath the Earthman's apparent surrender. She veiled her own eyes with long lashes, lest they betray the captive's plan to the alert Rogan. Her lips moved silently; perhaps she was praying to her Great White One.

"Release him," the Rogan ordered, triumph in his bird-like, shrill voice. The metal hoops were unfastened. Dex stretched his outraged body, wincing with the pain of movement; then felt life and strength returning to him.

"Come with us to the motor," commanded the Rogan, his dull eyes glinting in antic.i.p.ation of learning the coveted secret that should add one more planet to the Rogan's tyranny.

Dex walked to the dismantled atomic engine with him. He walked slowly, pretending more stiffness and weakness than he really owned to. No use in letting his captors know that his resilient muscles were so quickly throwing off the torment of the rack.

As he walked he kept his gaze covertly on that shock-tube that dangled in the leader's grasp. The rest of the guard had none; they had laid their weapons down on a far bench on their entrance to the chamber, depending on the one with which their leader was armed.

Eagerly the Rogans crowded around Dex and the motor that had thus far baffled them. They bent down from their twelve-foot heights to bring their staring goggle-eyes closer to the lesson in atomic motive power, till Dex was in a sort of small dome of Rogans, with their long, pipe-like legs forming the wall around him, and their thin torsos inclining forward to make a curved ceiling over him.

The Rogan leader drew Greca within the circle to interpret the Earthman's explanations.

Dex moved a trifle, to bring himself nearer the tall leader. Again he glanced covertly at the shock-tube.

"The first thing to tell about our motor," said Dex, stalling for time, "is that it utilizes the breaking up of the atom as its source of power."

He edged closer to the Rogan leader.

"You see those electrodes?" he said, pointing to two copper castings in a chamber between the fuel tank and the small but enormously powerful turbine that whirled with the released atomic energy. The Rogan leader blinked a.s.sent. His small, horrible mouth was pursed with his concentration of thought.

"The electrodes partially break down the atoms of fuel pa.s.sing from the tank," explained Dex, desperately attempting scientific phraseology for a matter as far over his head as the remote stars. He raised his hand a trifle, bringing it nearer the Rogan's tube....

"Is that the outlet from the tank?" inquired the Rogan, pointing with the tube, and so raising it out of Dex's reach.

"Yes," mumbled Dex, sick with disappointment: he'd been on the point of leaping for the weapon. He sidled close again. Greca bit her lips lest she cry out with suspense.

"The partially disintegrated atoms pa.s.s into the turbine chamber," he went on, "and are there completely broken down by heat, which has been generated by the explosive energy of the atoms pa.s.sing in before them."

"I warn you to speak true," said the leader, suddenly removing his gaze from the specimen motor and staring icily down at Dex. Dex's hand dropped abruptly from its place near the tube. Again his fingers had come within a foot of it.

"We will get ahead faster," piped the Rogan, an edge of suspicion sounding in his shrill voice, "if I conduct the explanation. I will ask questions for you to answer. What is the fuel used?"

"Powdered zinc," Dex answered promptly. No harm in admitting that. The Rogans must already know it; zinc was common to Jupiter, as Earth spectroscopes had showed long since; and they had no doubt a.n.a.lyzed it by now. The chances were that the leader was merely testing him, to see if he were sincere in his ostensible surrender.

That his guess was right, he read in the fishy, dull eyes. The Rogan leader nodded at his answer, and some of the lurking suspicion in his gaze died down.

"How is it prepared?"

Now this marked the beginning of the end, Dex knew. The preparation of the powdered metal was half the secret of atomic power--and Dex hadn't the faintest idea what it was! This questions-and-answers affair was going to pin him down in short order!