He became desperately economical of every watt of energy. He used power for the Disciplinary-Circuit beams which kept the enemy crew helpless and for the grapples which kept the two ships in contact--for nothing else. But still the lights flickered. The engines gasped for power. They started and checked and ran again, and again checked. The second they failed finally, the immobile monster alongside would become a ravening engine of destruction. The two men in the _Starshine_ would die in an instant of unspeakable torment. Dona--now fumbling desperately through unfamiliar passage-ways amid contorted, glaring figures--would be at the tender mercy of the crew. And when the three of them were dead the drive of the _Starshine_ would be at the disposal of the Empire of Greater Sinab if they only chose to look at it. The beastly scheme of conquest would spread and spread and spread throughout the Galaxy and enslave all women--and murder all human men not parties to the criminality. The lights flickered again. They almost died and on the _Starshine_, Kim clenched his hands in absolute despair. On the enemy warship the immobile crew made agonized raging movements. But the engine caught fugitively once more, and Dona worked desperately and then fled toward the airlock with her booty while the Disciplinary Circuit field which froze the Sinabian crew wavered, and tightened, and wavered once more. And died! Dona dragged open the enemy's inner airlock door as a howl rose behind her. She flung open the outer as murderous projectors warmed. She clattered along the outer hull of the Sinabian ship on her magnetic shoes, and saw the _Starshine_ drifting helplessly away, even the grapples powerless to hold the two bodies together. At that sight, Dona gasped. She leaped desperately, with star-filled nothingness above and below and on every hand. She caught the _Starshine's_ airlock door. And Kim cut out the Disciplinary-Circuit beams and the flow of current to the grapples and, with a complete absence of hope, pressed the transmitter-drive button. He had no shred of belief that it would work. But it did. The equalizer-batteries from the engines gave out one last surge of feeble power--and were dead. But that was enough, since nothing else drew current at all. The stars reeled. This was a test. Almost anything could happen. Kim held his breath, anxiously watching and waiting for the worst, his senses attuned to the delicate mechanisms about him. And then, slowly, the reaction was fully determined, and he smiled. 5 _The Needed Fuel_ The "_Starshine_" had a mass of about two hundred tons and an intrinsic velocity of so many miles per second. When the field went on, her mass dropped almost to zero, but her kinetic energy remained the same. Her velocity went up almost to infinity. And the Universe went mad.