to make the trips to the other places in the solar system from which the Sun-stealers are working. It is with this one vessel only that we can put their Sun-tap stations out of commission. "But I emphasize again the experimental nature of this ship. What its capacities are and how well it will work is still a matter of planning-book conjecture. We can prepare the ship to take off in one week's time. I do not think, judging from what Merckmann and Clyde have said, that we can afford to wait any longer. Another such ship cannot be built in less than a year." General Shrove spoke then. "It is already arranged that this A-G 17 spaceship is going to go. A volunteer crew has been selected; several of them are in this room." He nodded briefly to Clyde and to Lockhart. "But although these volunteers are among the best men in their fields, there isn't one of them who couldn't be replaced by someone equally skilled in the same field. But there is one person on Earth right now who may just possibly be unique. This person may hold, by virtue of an experience not shared by any other human being, a special key that will render easier the task that this spaceship must fulfill." He turned to Burl, who sat tingling with suspense. "You, Burl Denning, are apparently still carrying some sort of electronic or subelectronic charge which is attuned to the controls of the Sun-tap station. We feel that you should be along on this expedition. It will be long and dangerous, it will involve landings on worlds no man has ever visited or expected to visit for hundreds of years. There is an enemy in the sky who will certainly try to stop our single ship. To be bluntly honest, the voyagers on this ship face such dangers as explorers have not faced since the days of Magellan and Cook. Its chances of return are probably remote. But with the permission of your father, which he has already given, I would like to ask that you volunteer to join its crew." Burl felt dizzy, his heart thumping painfully within his chest. He took a deep breath, and then carefully, trying to keep his voice from quivering, he said, "Yes, I'll go." Chapter 4.The Hidden Skyport Around the table there was a concerted sigh. Burl, his ears still throbbing from his sudden excitement, realized each of them had been holding his breath. General Shrove smiled and glanced at the elder Denning, who sat expressionless. It is not an easy thing for him, Burl thought. At that moment, Burl knew that he had come of age. This moment of