Zyzz is a botany professor at a major university on Venus who gets drawn into a radical environmental group. He marries Zilla, one of his students, and they have two daughters. The group soon finds themselves in big trouble with the authorities as they draw attention to increasing evidence that Venus is in imminent danger, and propose solutions that run counter to the Establishment's interests. The government moves to quash the outcry, and arrests begin. Some radicals are banished to extra-Venusian penal colonies. As the planet's life-support system goes critical, difficult decisions must be...