Men had died. Some had died before they reached the Moon, some had died on the Moon but mostly they had died heading back for Earth. For landing on Earth, jockeying a rocket through Earth's dense atmosphere, is a tricky job. Others had died enroute to Mars, ships flaring in space or simply disappearing, going on and on, never coming back. That was the way it had been with Hugh. And now his brother, Scott, was following the trail that Hugh had blazed, the trail to the Moon and out beyond. Following in a bomb of potential death, with a blank-faced stowaway in the chair beside him. * * * * * Half way to Mars and the ship was still intact. Running true to course, running on schedule, flashing through space under the thrust of momentum built up during the blast-out from the Moon. Half way to Mars and still alive! But too early yet to hope. Perhaps other men had gotten as far as this and then something had happened. Scott watched the depths of space, the leering, jeering emptiness of star-studded velvet that stretched on and on. There had been days of waiting and of watching. More days of waiting and of watching loomed ahead. Waiting for that warning flicker on the instrument panel, that split second warning before red ruin struck as cranky fuel went haywire. Waiting for the "tick" of a tiny meteor against the ship's steel wall ... the tiny, ringing sound that would be the prelude to disaster. Waiting for something else ... for that unknown factor of accident that would spatter the ship and the two men in it through many empty miles. Endless hours of watching and of waiting, hastily snatched cat-naps in the chair, hastily snatched meals. Listening to the babbling Jimmy Baldwin who wondered how his flowers were getting on, speculated on what the boys were doing back in the rocket camp on Earth. One thing hammered at Scott Nixon's brain ... the message of the Martian radio, the message that had been coming now for many years. "_No. No. No come. Danger._" Always that and little else. No explanation of what the danger was. No suggestion for circumventing or correcting that danger. No helpfulness in Earthmen's struggle to cross the miles of space between two neighboring planets. Almost as if the Martians didn't want Earthmen to come. Almost as if they were trying to discourage space travel. But that would hardly be the case, for the Martians had readily co-operated in establishing communications, had exhibited real intelligence and earnestness in working out the code that flashed words and thoughts across millions of miles. Without a doubt, had they wished, the Martians could have helped. For it was with seemingly little effort that they sent their own rockets to earth.