Dr. Patrick Nolan, an anthropologist at Southern Arizona State University, accompanies a few of his colleagues on a trip to Cimmeria, an ancient civilization the anthropologists conjecture and imagine into a modern country. They create Cimmeria based on ancient accounts of the Indo-European country, but when they travel there, they find that the Cimmerians believe that their nation has existed for three thousand years. Cimmeria has a unique language, culture, set of customs, and international relations that make it appear real, but which were inspired by the American anthropologists.

Dr. Nolan, also known as Pat, explores the Cimmerian culture and discovers that Cimmerians do not recognize twins. Rather, they believe that a human being has a soul and that twins are one soul in one body. Thus, a twin is one person: the primary human and their shadow.

Pat meets and marries Shaila, a princess of Cimmeria who is also a twin. As Cimmeria becomes politically unstable, he travels to America with Shaila and her shadow self, settling comfortably into a marital life that does not truly recognize the existence of the shadow Shaila. But when Pat returns from work one day, he sees that the primary Shaila is gone and the shadow Shaila has taken her place. Unable to report Shaila as missing—after all, Shaila is still there—he continues his marriage and returns to Cimmeria where (shadow) Shaila births his son and rules the nation.