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 assent, 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 anticipation 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."