Shapiro's Mumps spread over the entire planet in the next few decades. It leaped across every quarantine erected; for a long time, it successfully defied all the vaccines and serums attempted against it. Then, when a vaccine was finally perfected, humanity discovered to its dismay that its generative powers had been permanently and fundamentally impaired. Something had happened to the germ plasm. A large percentage of individuals were born sterile, and, of those who were not, one child was usually the most that could be expected, a two-child parent being quite rare and a three-child parent almost unknown. Strict eugenic control was instituted by the Security Council of the United Nations so that fertile men and women would not be wasted upon non-fertile mates. Fertility was the most important avenue to social status, and right after it came successful genetic research. Genetic research had the very best minds prodded into it; the lesser ones went into the other sciences. Everyone on Earth was engaged in some form of scientific research to some extent. Since the population was now so limited in proportion to the great resources available, all physical labor had long been done by robots. The government saw to it that everybody had an ample supply of goods and, in return, asked only that they experiment without any risk to their own lives--every human being was now a much-prized, highly guarded rarity. There were less than a hundred thousand of them, well below the danger point, it had been estimated, where a species might be wiped out by a new calamity. Not that another calamity would be needed. Since the end of the Epidemic, the birth rate had been moving further and further behind the death rate. In another century.... That was why a desperate and secret attempt to alter the past was being made. This kind of world was evidently impossible. Max Alben finished the manuscript and sighed. What a wonderful world! What a comfortable place to live! He walked to the rear dials and began the process of materializing at the crucial moment on April 18, 1976. _flick!_ * * * * * It was odd, Mac Albin reflected, that these temporal journeys, which induced coma in everyone who tried it, only made him feel slightly dizzy. That was because he was descended from Giovanni Albeni, he knew. Maybe there was some genetic relationship with his above-average fertility--might be a good idea to mention the idea to a biologist or two when he returned. _If_ he returned. All around the time machine, there was a soupy gray murk in which objects were hinted at rather than stated definitely. It reminded him of the problems of landing a helicopter in a thick fog when the robot butler had not been told to turn on the ground lights.