Baley's memory remains in the mind of his former lover, Gladia Delmarre, a long-lived "Spacer" who uncharacteristically relocated from the spacer world of Solaria to Aurora. Gladia's homeworld and the 50th-established of the Spacer planets, Solaria, has become empty of all human inhabitants, although millions of robot servants remain. A seventh-generation descendant of Baley's, Daneel Giskard ('D.G.') Baley, gains Gladia's help in visiting Solaria, to investigate the destruction of several "Settler" spaceships that made landings there, and to capture the presumably unsupervised robots. Gladia is accompanied by the positronic robots R. Daneel Olivaw and R. Giskard Reventlov, both the former property of their creator, Dr. Han Fastolfe, who bequeathed them to Gladia in his will. R. Giskard has secret telepathic powers of which only R. Daneel knows.