This story is the second step in the long friendship between the earthling New York detective Elijah Baley and the robot detective R. Daneel Olivaw.
Situated in a far future Earth, Humankind has divided into Spacers who dwell scattered in fifty worlds (and are the rich and advanced society) and Earthlings that remain in the Mother World, inhabiting overcrowded underground cities. Both groups distrust and despise each other.
A murder occurred in Solaria, an Outer World. Elijah is put in charge of the investigation due to his success in the previous investigation. He will team with R. Daneel, a robot.
Bailey is terrorized to be outside of the caves. From that fact derives the title of the novel as the Naked Sun is almost unbearable to stand for him.
The Solarians avoid direct contact with other humans. They interact thru holographic system and are surrounded and served by robots that do not look like humans. Imagine in this context how a crime is possible. Well that is the task of our heroes.
Early Asimov. 1957. The 3Laws and humans with phobias conditioned by their lack of exposure to 'others' ways. Bailey is from Earth where the fear is of living on the surface. Solaria is ALL surface living. However, it is so under populated, that Solarians fear physical closeness, having so seldom even seen another Solarian face to face. Chores and caretaking of infants are done by their many robots after all. So how could one get close enough to another to bludgeon them to death?