The story takes place during the process of Trantor's rise from a large regional power to a galaxy-wide empire, unifying millions of worlds.

The relationship between the two planets is analogous to that between European imperial powers and their colonies during the 19th century, or the owners and slaves on the cotton plantations of US South: native Florinians are forced to work in kyrt fields and are treated as an inferior race by the resident Sarkites.

Ultimately he learns that before losing his memory he was a "spacio-analyst": a specialized astronaut who gathers samples of the very sparse interstellar gasses in outer space, and determines their composition.

He also finds out that he had discovered that Florina's sun is about to explode into a nova because it is being exposed to a stream of isolated gaseous carbon atoms flowing through its region of space.

His amnesia was caused by the blackmailer's misuse of a mind-altering device called a "psychic probe" in an attempt to calm him down before he could seek other means to make it public.

However, once Rik recovers his memory and reveals the effect of the carbon atoms, the conditions that enable kyrt to grow are understood and can be easily duplicated anywhere.

To drive home the point, an official of the Interstellar Bureau of Spatio-analysis (IBS) who is trying to locate the missing Spatio-analyst is noted as being from the planet in the galaxy with the darkest average skin color and wooly hair.

"[2] "Asimov has the cotton plantations of North America in mind when describing conditions in Florina but has cunningly reversed the complexions of master and servant.