There followed some anxious hours, which Dynamon spent with his eyes glued to the periscope mirror. In a short time the early golden rays of the sun appeared, and the Martian Carrier followed behind inexorably, glowed an ugly menacing crimson. Once Dynamon instructed his communications officer to speak to the Martian ship. "Lovely morning, Mars. Where are you bound for?" was the casual message. There came back a terse answer, "Test flight, and you?" "We're testing, too," Dynamon's communications officer said. "We'll show you some tricks up beyond the stratosphere." All so elaborately casual, Dynamon thought grimly. It was fairly evident that the Martian ship intended to follow the Earth Carrier to find out where it was going. Those inhuman devils! Why did the Earth's people ever have to come in contact with them? Dynamon's thoughts went back to his childhood, to that terrible time when the men of Mars had abruptly declared war and descended suddenly onto the Earth in thousands of Cosmos Carriers. Only the timely invention of that remarkable substance, Geistfactor, had saved Earth then. It was a creamy liquid, which spread over any surface, rendered the object invisible. The principle underlying Geistfactor was simplicity itself, being merely an application of ultra high-frequency color waves. But it saved the day for Earth. The World Armies, cloaked in their new-found invisibility, struck in a dozen places at the ravaging hordes from Mars. The invaders, in spite of their prodigious intellectual powers, could not defend themselves against an unseen enemy, and had been forced to withdraw the remnants of their army and sue for peace. But the unremitting jealousy and hatred of the little men with the giant heads for Earth's creatures was leading to new trouble. It enraged the Martians to think that human beings, whom they despised as inferior creatures, should have first thought of spanning the yawning distances between the planets of the solar system. It was doubly humiliating to the Martians that when they, too, followed suit and went in for interplanetary travel, they could do no better than to copy faithfully the human invention of the Cosmos Carrier. It was only too evident that Mars was gathering its strength for another lightning thrust at the Earth. This time, with the Photo-Atomic Ray, there was no doubt that they intended to destroy or subjugate Earth's peoples for good. And to that end the Martians had been inventing new bones of contention and had been contriving new crises. A peace-minded World Government had been trying to stave off the inevitable conflict with conference after conference. But to those on the inside it was only too evident that the Martians could invent pretexts for war faster than Earth could evade them. * * * * *