Councilman Golan Trevize, historian Janov Pelorat, and Bliss of the planet Gaia (introduced in Foundation's Edge) set out on a journey to find humanity's ancestral home planet—Earth.

The purpose of the journey is to settle Trevize's doubt of his intuitive endorsement, at the end of Foundation's Edge, of the all-encompassing noosphere of Galaxia as the future of mankind.

Next, they visit Solaria, where they find that the Solarians, who have survived the Spacer-Settler conflicts by clever retreat detailed in Asimov's novel Robots and Empire, have genetically engineered themselves into self-reproducing hermaphrodites, generally intolerant of human physical presence or contact.

They have also given themselves the ability to mentally channel ("transduce") great amounts of energy obtained from their vast estates via a modification to the brain, and use this as their sole source of power.

Wearing space suits, they enter a library, and find a plaque listing the names and coordinates of all fifty Spacer worlds.

The natives appear friendly, but secretly they intend to kill the visitors with a microbiological agent to prevent them from informing the rest of the galaxy of their existence.

They are warned to escape before the agent can be activated by a native woman who has formed an attraction to Trevize and was impressed by Fallom's ability to play a flute with just her mind.

There, they find R. Daneel Olivaw, who explains he has been paternalistically manipulating humanity since Elijah Baley's time, long before the Galactic Empire or Foundation.

Trevize then confirms his decision that the creation of Galaxia is the correct choice, and gives his reason as the likelihood of advanced life beyond the galaxy eventually attacking humanity.

Trevize states that there should be enough time for Galaxia to be fully ready as long as the enemy is not already present among them, not noticing Fallom's alien gaze resting unfathomably upon him.

Dave Langford reviewed Foundation and Earth for White Dwarf #84, and stated that "Whopping concepts and evocative descriptions boost the novel half-way to excellence, but are defeated by the dead-weight of the stereotypes and lecturing.