When AIVAS -- the Artificial Intelligence Voice Address System -- was first discovered at Landing, the enture planet of Pern was awed at the knowledge it divulged. All the history of the people of Pern was there. Dragonholders, Lord Holders and Craftmasters crowded into the tiny inner room to learn the secrets of their beginnings. Ana AIVAS had other gifts to offer -- stored information of old crafts that had been forgotten, of medicine, music and technology. Bu the greatest promise AIVAS offered was the chance to rid Pern of Thread forever. All the great ones of Pern began the long and arduous task of learning just how to operate the incredible plan -- a plan of such daring and epic proportions that both dragons and riders would be put at risk.