The second novel in the Southern Reach trilogy, Authority picks up after the events of the first novel, Annihilation. Annihilation follows an unnamed biologist as she sets out on the 12th expedition into Area X, which is a bizarre, ecologically mysterious area of land with a shimmering border. She volunteered for the mission after her husband returned from the 11th expedition, a secretive military mission, one year after leaving. Most of the other people who had explored Area X never returned; many experienced hallucinations while there or killed each other. The biologist’s husband remembered little of Area X. He died of cancer soon after his return, which spurred the biologist to explore Area X.

Expeditions into Area X are led by a government agency known as the Southern Reach. The Reach trains the biologist and three other women, a psychologist, an anthropologist, and a surveyor. The all-women team enters the eerie border of Area X. After days of hiking through the wilderness, they find The Tower, an underground tunnel. The Tower’s walls have strange writing in bioluminescent plant material, and they also notice tracks. While studying the tunnel, the biologist inhales spores from the plants on the walls. These spores later transform her into a part of Area X, making her glow, giving her immunity to hypnosis, heightening her senses, and allowing her to heal quickly.