The story is set at an unspecified point in the future in a community called Latimer on a planet called Lacanth C. The planet was discovered simultaneously by humans and an alien race called the Snarre't over 150 years prior to the story's setting, and, rather than going to war, both agreed to rule the planet as a codominium, and colonists from both civilizations soon established themselves there. In addition to their substantial physiological differences, the Snarre't also rely on biotechnology, rather than the mechanical technology Earth uses.
The story focuses on human police sergeant John Paul Kling and a Snarre' investigator called "Miss Murple" (the closest approximation to her name human language is capable of), who are required to work together to investigate the birth of a human child born with substantial deformities. The deformities are so severe that human authorities fear that the child was the victim of a Snarre'i hoxbomb, a biotech weapon. Such an action could prove a diplomatic nightmare for both peoples.
The name "Snarre't" is "terrans" spelled backwards. Terran is a common demonym for humans in science fiction works. The backward spelling further emphasizes the dark mirror each species represents to each other. Similarly, Snarre't culture and technology make use of backwards or analogous naming conventions. For example, their modes of transportation include "caitnops" and "drofs", the backwards spelling of Pontiac and Ford.