When that took place it was the duty of the Bureau of Operations to detect them, to intercept them, and to warn the men of Earth, Sol, that Mankind was no longer alone. The fact that the subelectromagnetic detecting beams had been sweeping space for a couple of hundred years without detecting anything had no bearing on the future. The beams must be maintained so long as a human man remained alive in space. In addition to the detector beams, the outlying planets carried astrogation beacons. They were subelectromagnetic lighthouses, so to speak, that rang across space with known direction and ranging telemetered signals. Someday, Man hoped to fill the space lanes with spacecraft and the planets with interstellar commerce. Someday there might be another _Marie Celeste_ plying its course with its crew inexplicably missing. But if this ever happened, it was not going to happen without the Space Service knowing precisely how many and which spacecraft were operating through that volume of space before, during, and after D-for-Disaster Day and M-for-Mysterious Minute. The equipment, of course, was automated to modern perfection, with multi-lateral channels that would take over in case of component failure. Its factor of reliability was well above six or seven nines of perfection. But to admit that this perfection was adequate would have deprived the Space Service of a convenient minor penal detail to take care of brash junior officers. Manning such a station provided the junior officer with a wealth of time to contemplate his sins, and to mend his evil ways. In the case of Junior Spaceman Howard Reed, this process consisted of locating the flaw that prevented Hansen's Folly from being Hansen's Analysis. * * * * * Now, from the time of Alexander Selkirk, romantic history has been dotted with accounts of men who have been cast away with nothing more than their hands and their brains. And with these, they have succeeded in raising their caveman environment up to the level of modern technical conveniences. Like them--having been unable to locate the flaw in Hansen's Folly by the theoretical approach during his tour of duty on Earth, Sol, and having similarly failed to locate the error in experimental hardware during his tour of duty on Eden, Tau Ceti--Junior Spaceman Howard Reed began to experiment on the spacecraft that stood parked on its launching pad two hundred feet from the Installation. There was plenty of equipment to work with. The Space Service did not stock its perimeter stations in a slipshod manner. Furthermore, Junior Spaceman Howard Reed had plenty of time. The account of his life and adventures is hardly worth telling. He had no distractions. He worked. The months passed one after the other.