Adelpha is the parallel world into which Cutter Slade the hero is cast. It is a planet located in a universe which exists alongside our own and where communications with Earth were established through the scientific experiments of Kauffman and Xue. Adelpha was christened by these two scientists based on their first impressions of an environment very similar to that on Earth, hence the idea of a sister planet (Adelpha in Greek). Its morphology and ecosystem are very similar to those of our own planet except that it orbits around a double star. Consequently there are two suns in the sky above Adelpha. In addition, since two satellites orbit the planet, there are two moons which light the night sky. The Regions or "Worlds" Adelpha is made up of large regions: they differ so greatly one from another that they are also called "Worlds". Although strictly incorrect, this term reflects the variety and contrast between each of these landscapes.