The Land Without Stars

When a wandering planet threatens a Terran colony, Valerian and Laureline investigate. The world is divided among nomads who harvest energy-bearing plants; a city entirely ruled by men; and a city entirely ruled by women. Convincing the groups that their world is doomed, Valerian gets them to work together and pool their stocks of energy-producing plants. Valerian uses their destructive power to push the planet into a stable setting. The male emperor and female queen unite their people by joining in marriage.