Imagine that your planet is faced with imminent destruction from space. Not from a sentient or malicious attack, but from a mindless threadlike worm falling from the sky to devour any carbon based material in it's path. The only thing that can protect Pern from the devastation Thread brings are fire breathing dragons especially bred to flame the Thread from the sky before it touches ground. The problem is there are far too few dragons to protect the whole world.
In this first of the Dragon Riders of Pern series, the story begins with Lessa. The youngest daughter of the noble rulers of Ruatha, Lessa has been living in hiding since her family was murdered in a policial coup ten years ago. When Dragonriders come to Ruatha with news that the last Dragon Queen has eggs ready to hatch, she tricks them inot fighting the murderer of her family, Fax, to a duel. Fax is killed in the duel, but the Dragonriders convince her to leave the rule of the Hold to Fax's infant son because she is needed as a Dragonrider.
The dragons have been bred to have a lifelong mind link with their human riders, called impression. The link begins at birth as soon as the eggs hatch and does not end utnil either Dragon or rider are dead. A Dragon suicides when his rider dies. Dragons not only have the ability to breath fire, they have the ability to teleport between places so they can move quickly out of the way of thread to "between". Lessa is brought onto the hatching ground with several other young girls where she "impresses" Ramoth, the newest and now only dragon queen on Pern.
Lessa soon finds that life as the Queen Dragonrider is not what she expected. Most of the inhabitants of Pern do not think that Thread will ever fall again; after all it has not happened in almost four hundred years. Even some of the Dragonriders do not believe in Thread after all this time. But other Dragonriders are seeing the signs that their ancestors had said foreshadowed the coming of Thread. The problem is there are not enough Dragons. When Thread finally does begin to fall, the problem becomes accute. Lessa thinks she has found an answer. In the past there had been thousands of Dragons where now there are only a few, and Lessa has found that Dragons can teleport throught time as well as space. The problem is that teleporting through time even a short time causes the rider severe mental distress. Lessa ingnores the distress and using an ancient tapestry to give her a picture of Pern 400 years earlier, she travels back in time nearly dying along the way. Her trip is successful, however, and she brings back nearly two thousand Dragons and their riders to save the planet in her time.
This story is the first of two trilogies which tell the epic tale of how the inhabitiants of Pern finally defeat Thread forever. This first story is an epic in itself with a heroine who goes on an impossible quest to save her world and survives to tell the tale.