All the Weyrs of Pern

All the Weyrs of Pern, the twelfth novel in the Dragonriders of Pern series (counting Dragonsdawn as the first chronologically), was written by Anne McCaffrey and released in 1992. The plot picks up right after the events of Renegades of Pern, when an excavation at the Landing site uncovers the original colonists' Admin building and a sophisticated computer called AIVAS (Artificial Intelligence Voice Address System). This computer, untouched for about 2,500 years since the original colonization (roughly 2,500 years after the events of Dragonsdawn), holds a vast store of lost knowledge and claims it can permanently end the threat of Thread. Led by Lessa and F'lar, the Weyrs embrace this opportunity. With backing from the Holds—especially Jaxom—and the Crafthalls, championed by Masterharper Robinton, they follow AIVAS's plan. The computer, programmed with a humorous, masculine-like personality, is understood by the Pernese as a machine and artificial intelligence from the original colonists, though its advanced knowledge and personality still inspire awe. Over four years, Pernese society recovers many lost technologies, including electricity, plastics, heating and cooling, printing presses, and surgery. While most efforts focus on eliminating Thread, medicine and science also advance greatly, leading to new Crafthalls such as the Print Hall, Paper Hall, Computer Hall, and later the Dolphin Hall (a story continued in The Dolphins of Pern). These rapid changes cause culture shock. Some traditionalists label AIVAS an "Abomination" and try to sabotage it and its projects. This resistance culminates in the kidnapping of Masterharper Robinton, with the kidnappers demanding AIVAS's destruction in exchange for his life. The conspirators—two Lord Holders and a Craftmaster—are caught and exiled. The Weyrs, Holds, and Halls then succeed in AIVAS's plan: they transfer fusion drives from the original colony ships to the Red Star and detonate them. The explosion shifts the Red Star's orbit, preventing Thread from reaching Pern. AIVAS reveals to Jaxom that success requires him to lead other Dragonriders in using the rare ability to travel through time. He must deposit two of the three engines 1,800 Turns and 600 Turns in the past (relative to the story's present), so that the combined effect of three explosions alters the planet's orbit.