To his chagrin, Detective Elijah Baley must leave Earth to investigate a murder on the sparsely populated outer world of Solaria where crime is practically nonexistent and robots far outnumber their human masters. In fact, humans on Solaria have evolved into isolationists, communicating with one another solely by holographic projection, otherwise known as “viewing.” The mere suggestion of physical contact or even close proximity is taboo—even for married couples.

This custom only complicates Baley’s investigation into the murder of biologist Rikaine Delmarre. Allegedly alone in his lab at the time, Delmarre was found bludgeoned to death with his wife, Gladia, lying unconscious beside him and a malfunctioning robot standing over them. Gladia is the prime suspect simply because she was the only person Rikaine would permit to see him. Certainly, the robot could not blamed, as robots cannot kill humans. Baley is not convinced, especially since no weapon has yet been found.

What of the robot? Solarian robots are constructed with positronic brains, programmed with the Three Laws of Robotics—a robot may not injure a human being or, through inaction, allow a human being to come to harm. A robot must obey orders given it by human beings except where such orders would conflict with the First Law. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

Further inhibiting Baley’s investigation is his innate fear of the outdoors, resulting from a lifetime in the enclosed, underground cities of Earth. However, Baley forces himself to cope as he journeys across Solaria with his partner, R. Daneel Olivaw to interview various people in Delmarre’s life. A robot indistinguishable from a human, Olivaw was assigned to the investigation from the planet Aurora, another of Earth’s colonies.

With all of these impediments—and more—Baley must delve into Solarian sociology and psychology in his quest to compile the evidence needed to bring the murderer to justice.

The Naked Sun is the second of Asimov’s four robot novels starring Elijah “Lije” Baley and R. Daneel Olivaw (who also appears in Asimov’s Foundation series). The story’s title is derived from the fact that, in Asimov’s future, citizens of Earth live underground and have developed a dislike of the outdoors and have not set eyes on their own sun in many generations.

While Asimov has never been known for the depth of his characters, the human sociological idiosyncrasies of Baley, as juxtaposed against those of the Solarians, added another level of tension and complexity beyond a mere murder investigation.