A mom and also her 3 children-- charming Bee, reasonable Evie, and also kid of nature Sissy-- inhabit the titular glass building, which has been totally sealed off to safeguard its owners from a dementia-inducing contaminant called the Shred that's poisoning the air outside. Frightened of becoming like the shed spirits who stray the void outside, the household keep a grasp on their past by executing spiritual routines. When damages the rules and also lets a damaged complete stranger into their midst, the family dynamic is ruined for life, as concealed truths overthrow the impressions the ladies have actually functioned so hard to secure.