The main scope of this book is to reconcile two of Asimov's main series, the Robot series and the Empire series (continued later in the Foundation series). That is, to understand the transition from a mixed humanity-robot universe, dominated by the increasingly robotic societies of the Spacer Worlds, to a human-only Empire.
Elijah Baley, the hero of the previous books, died two centuries ago. But his memory remains in the mind of his lover Gladia who, as a Spacer, has a much longer life. She meets a fifth-generation descendant of Elijah, and together they start a tour of the new worlds settled by Earth. Evidence is that some Spacer worlds are decaying, and especially Solaria seems deserted. At the same time, they fight a covert war with Elijah's archrival Kelden Amadiro, still alive. Amadiro and his young fellow roboticist have a deadly plan for Earth: using sophisticated technologies, increase its radiation level to render it unsuitable for human life. Gladia's robots, R. Daneel Olivaw and Giskard, fly to Earth to stop them, but Giskard has developed some unprecedented abilities that will help him, and his friend Daneel, to orchestrate the future history influencing key people in both Earth and on Spacer worlds. Those who read Asimov's Empire books already know about the Earth's fate...Plot