And if anything had happened to Dad.... * * * * * The sun was sinking rapidly toward the horizon when the city finally came into sight in the distance, but try as he would, Tom Hunter could not urge more than thirty-five miles an hour from the huge lurching vehicle he was driving. On an open paved highway the big pillow-wheeled Sloppy Joe would do sixty in a breeze, but this desert route was far from a paved road. Inside the pressurized passenger cab, Tom gripped the shock-bars with one arm and the other leg, and jammed the accelerator to the floor. The engine coughed, but thirty-five was all it would do. Through the windshield Tom could see the endless rolling dunes of the Martian desert stretching to the horizon on every side. They called Mars the Red Planet, but it was not red when you were close to it. There were multitudes of colors here ... yellow, orange, brown, gray, occasional patches of gray-green ... all shifting and changing in the fading sunlight. Off to the right were the worn-down peaks of the Mesabi II, one of the long, low mountain ranges of almost pure iron ore that helped give the planet its dull red appearance from outer space. And behind him, near the horizon, the tiny sun glowed orange out of a blue-black sky. Tom fought the wheel as the Sloppy Joe jounced across a dry creek bed, and swore softly to himself. Why hadn't he kept his head and waited for the mail ship that had been due at the Lab to give him a lift back? He'd have been in Sun Lake City an hour ago ... but the urgency of the message had driven caution from his mind. A summons from the Mars Coordinator of the U.N. Interplanetary Council was the same as an order ... but there was more to Tom's haste than that. There was only one reason that Major Briarton would be calling him in to Sun Lake City, and that reason meant trouble. Something was wrong. Something had happened to Dad. Now Tom peered up at the dark sky, squinting into the sun. Somewhere out there between Mars and Jupiter was a no-man's-land of danger, a great circling ring of space dirt and debris, the Asteroid belt. And somewhere out there, Dad was working.