"Take off!" The command whipped out and Jeffery's fingers flashed over the rows of keys with automatic precision. For the fraction of a second there was a muffled, rumbling thunder. Then, both Dennis Brooke and Jeffery were slammed back against their air-cushions as the astounding crescendo of acceleration hit them. Twisting his head slowly, Captain Dennis looked at his navigator in astonishment. Tom Jeffery had always been the acme of dependability, his precision in plotting had practically become a legend in the I.S.P. "Cruiser's running wild!" Jeffery gasped painfully. "The key bank must ... be out ... of order. I'd never ... never use that much speed on take-off!" "Slack off...." Dennis gritted. He saw Jeffery struggle to get his long, supple hands back on the keys. Blood throbbed and pounded in surging waves at his temples, and he knew he'd black out in a matter of seconds if his Navigator didn't reach those keys. Concentrating all his remaining energy, Jeffery reached and pushed one hand forward, but it was like pushing against an invisible wall. His hand refused to move any further, and then he felt the impenetrable blackness welling up inside his brain. Nervelessly the Navigator's hand dropped, but two fingers scraped over the key-bank and the flashing cruiser changed its course. The ship angled upward sharply and gradually reduced its speed. Like two punch-drunk mortals, Dennis and Jeffery shook their heads, doggedly trying to clear the clinging black webs from their brains. They were not unnerved, for to these two, danger was too familiar a face, it was a constant shadow at their heels, the eternal companion at their table--without it, life would have seemed flat, without zest. "Worse than a shot of Martian _Absytron_! Whew!" Jeffery exclaimed, startled out of his usually laconic state. "That mineral's terrific!" "I was just thinking the same thing," Captain Brooke agreed quietly. "Which makes it doubly important that we settle scores with Koerber and leave this planetoid. If the reaction of this mineral's true, we've found a new type of fuel, far more powerful than anything known to us at present." "Imagine if that space-rat gets hold of it," Jeffery concurred in awed tones. "He could rule the space-lanes, commit any crime and outpace any ship in the universe!" "Besides," Dennis said ruminatively, "this mineral'd make Terra independent of Venus for her supply of radio-actives. It would usher in a new era, Jeffery!"