When Masterharper Zist takes over as Harper for Natalon's coal-mining camp, he takes with him his apprentice, the orphaned, mute Pellar, and Pellar's fire-lizard Chitter. Pellar has become a gifted tracker and Zist gives him his own mission - to find out if the recent thefts of coal are the work of the Shunned, criminals condemned to a life of wandering and hardship. Halla is one of the children of the Shunned.

Though innocent of their parents' crimes, these children have inherited their cruel punishment. With no shelter when the lethal Thread falls again they will have no protection against it. Life is even tougher for Halla, all her family are dead and she must fend for herself.

Yet Halla is kind and gentle, devoted to helping those more helpless than she, unlike Tenim, a fellow child of the Shunned. Tenim is in league with Tarik, a crooked miner from Camp Natalon, who helps him steal coal in exchange for a cut of the profit. But Tenim soon realizes there is a lot more to be made from firestone, the volatile mineral that enables the dragons of Pern to burn Thread out of the sky.

Tenim doesn't care what he has to do, or whom he has to kill, in order to corner the market. Cristov is Tarik's son. Dishonored by his father's greed and treachery, he decides he must make amends somehow...even if it means risking his life by mining the volatile firestone, which blows up at contact with the slightest drop of moisture.

When the last remaining firestone mine explodes in flames, a desperate race begins to find a new deposit of the deadly but essential mineral, for without it there can be no defence against Thread. But Tenim has a murderous plan to turn the tragedy to his own advantage, and only Pellar, Halla and Cristov can stop him - and ensure that there will be a future for all on the world of the Dragonriders.