Ancient Pern is the fourth book in the Riders of Pern series and follows the novels Flight of the Dragon, Quest of the Dragon, and The White Dragon. The book contains two novels that make up a duology about the ancient times of Pern, approximately a thousand years distant from the era of F'lar and Lessa, described in the first three works. The Sixth Passage of the Scarlet Star ends; the flow of destructive Threads that tormented Pern for decades is becoming less frequent; Horsemen and dragons, residents of holds and workshops are anticipating the onset of peaceful times. And at this moment, a new disaster befalls Pern - a terrible epidemic brought into the habitable zone of the planet by a mysterious animal from the southern continent. The Horsemen, together with the Guilds of Harpers and Healers, are straining their last strength in search of an antidote; They travel through time and space, looking for a magical elixir. In these harsh days, the names of two women, Morita and Nerilka, became known to many; women whose dedication saved the lives of hundreds of people.