Canopus, a benevolent galactic empire centred at Canopus in the constellation Argo Navis, colonise a young and promising planet they name Rohanda (the fruitful). They nurture its bourgeoning humanoids and accelerate their evolution. When the Natives are ready, Canopus impose a "Lock" on Rohanda that links it via "astral currents" to the harmony and strength of the Canopean Empire. In addition to Canopus, two other empires also establish a presence on the planet: their ally, Sirius from the star of the same name, and their mutual enemy, Puttiora. The Sirians confine their activities largely to genetic experiments on the southern continents during Rohanda's prehistory (described in Lessing's third book in the Canopus series, The Sirian Experiments), while the Shammat of Puttiora remain dormant, waiting for opportunities to strike.