A mom and her three daughters — romantic Bee, smart Evie “Glasshouse”, and little one of nature Daisy — occupy the titular glass constructing, which has been utterly sealed off to guard its occupants from a dementia-inducing toxin known as the Shred that’s poisoning the air outdoors. Petrified of turning into just like the misplaced souls who wander the abyss outdoors, the household preserve a grasp on their previous by performing sacred rituals. When Bee breaks the foundations and lets an injured stranger into their midst, the household dynamic is shattered perpetually, as hidden truths upend the illusions the ladies have labored so exhaustingly to guard.