After Elijah Baley, the same plainclothesman from Earth, solved a case on Aurora, as he did on Solaria, the Earthmen began to leave their miserable planet and start settling new planets once more. They called themselves the Settlers.
They settled worlds in the millions, in the billions. In just a short time, there were more Settler worlds than there were Spacer worlds.
Some Solarians wondered at Gladia. Why would anyone want to leave Solaria? The thought seemed inconceivable, ludicrous! Leave such a perfect world as Solaria? This worried some very much.
Just as the Settler did. They flocked! However, the Solarians could see the failure there was in flocking. What if Solarians themselves took to it? After all, one had already left! But that must not happen again. Solarians would remain Solarians! Solaria would remain Solaria. The flaw was in the gene analysis in that particular woman. Leebig, as well. The best thing to do now, was to hide, they decided. Hide and figure out a way to solve their problems. But it would have to be a way that no one would know. Or find out. Or suspect.
It took almost twenty decades to finally perfect the nuclear intensifier. They also took an interest in building humaniform robots, and looked up all information they could on the one who had been on Solaria. And there would have to be a fail safe way to assure themselves that no one would be able to find them.
An Auroran, Vasilia Aliena, would be arriving. She was touring the Spacer worlds, finding how each was doing on robotics. They had no choice but to allow her to spend some time on Solaria. Not very much, hopefully. They would say nothing, of course.
Meanwhile, they worked. The mansions would be left on the surface, however, they would build another mansion underground on each estate.
Finally, after much work, they had the perfect humaniform. It would only obey a human being if that human being spoke with a Solarian accent. Anyone landing on Solaria would immediately be obliviated, and the Solarians would be safe. So they retreated to their underground mansions. It would give the appearance that they had left.
Two Settler ships arrived, and were taken care of by the robots. Another soon landed.