The story is set on a huge moon Medea, nearly the size of Earth, and the events take place in and near Port Kato on the island of Hansonia. Medea is in the system Castor C, also known as Colchis, which has the double suns Phrixus and Helle. The movement of the suns relative to Medea affect the rhythms of Medea's native life; in particular they trigger the mating of flying insectoids called glitterbugs.

The flying glitterbugs create shimmering swarms of light that the ouranids call "Shining Time," and the coming of Shining Time signals to the ouranids that it is time for some of them to fly across the ocean to icy wastelands where they will die and, according to their new religious faith, merge into a paradisiacal afterlife. It is this event that is the source of hostilities between the ouranids and dromids, the two intelligent...