The first section of Helliconia Spring tells the story of Yuli, who finds an underworld where a perverted religion” the virtual worship of darkness—holds sway. He works his way back to the world of day and founds a city called Oldorando. There, as the planet emerges slowly from its centuries-long winter, the tribes of the equatorial continent emerge from their hiding places. They begin to do battle, not only for survival but also to dispute possession of the planet with the ferocious phagors. In the central city, all the appurtenances of civilization—love, trade, coinage, history, and science” are being rediscovered. Yulis descendants hail him because he rejected his faith in favor of his people.
Other characters emerge in this episodic novel, which spans centuries. Helliconia eventually undergoes still another violent change as winter yields to a triumphant spring. Above the planet, five thousand astronauts from Earth orbit the planet in space station Avernus. They are prohibited from intervening in the affairs of Helliconia because some aspect of its atmosphere is poisonous to humans. They relay the day-to-day activities of Helliconia back to Earth, where Helliconian events have become a space opera on the Eductainment Channel.
Helliconia Summer covers a time span of only a few months. Its plot events center on the tortured king, Borlien, and his queen, Myrdem Inggala. Borlien, for political reasons, decides to divorce his queen and marry the princess of ancient Oldorando. The scene shifts rapidly from continent to continent until an Avernian Earthman, Billy Xiao Pin, attempts to intervene in the affairs of Helliconia, with predictably tragic and fatal results.
In Helliconia Winter, as Helliconia moves away from its larger sun, auguries of winter begin to haunt the planet. Snow falls, crops fail, and tyranny tightens under the sway of the Oligarch. On Helliconia, Luterin Shokerandt begins a pilgrimage of terror to the arctic regions of the planet. He enters the Great Wheel of Kharnabhar, where prisoners are supposed to row their planet back to light. This action has become almost a religious ritual, and all the trappings of the Darkness religion, first glimpsed in Helliconia Spring, are given new meaning. Coupled with the main story is the continuing saga of the observer space station, Avernus, and events on post-apocalyptic Earth that parallel those on Helliconia, separated by 1,500 light-years of time.