The Spacer world Persephone is in trouble. A mutation in the native life led to the collapse of Persephone's carefully managed environment. The atmosphere is now unbreathable and human life impossible outside of force-field-covered areas.

The Settler world of Echo is also troubled. The support for colonization was cut before the new ecology was stable. Without an additional injection of citizens the terraforming project will fail.

A plan was devised to overcome both worlds problems by relocating the population of Persephone onto Echo. For this to work, though, both sides will need to overcome the centuries-long mistrust between Settlers and Spacers, and deal with their cultural differences, especially with respect to the use of robots.