The fertile planet Pern, inhabited in ancient times by terrestrial colonists, is subject to regular disasters - invasions from space of filamentous spores that destroy any organic matter. The inhabitants of the planet, having forgotten the technical achievements of their ancestors, are fleeing the threat in stone cities - holds. But the main means of defense are the mighty, noble dragons, semi-intelligent creatures whose fiery breath burns deadly spores. However, only people gifted with telepathic abilities can understand dragons - and only they, the Riders, can save the beautiful Pern. But then came the time when there were almost no Horsemen or dragons left on the planet... A time when the terrible Threads again appeared in the defenseless skies of Pern.