The grim specter of disease has appeared in the Weyrs of Pern, bringing with it a potential danger to dragons, delightful fire-breathing creatures. Threatened by the arrival of a new, rapidly approaching Fall, from which dragons are the only defense, every Weyr on Pern has found itself in a crisis situation. Situation and The mood of the people in the Weyr worsens further when scouting parties bring news of the appearance of black dust - an unmistakable harbinger of the Fall. More and more dragons are weakening and dying, leaving only young animals in the Weyr who cannot help in any way. Is there any way to save the weakened dragons and the entire endangered planet?