M3GAN is a marvel of artificial intelligence, a life-like doll programmed to be a child's greatest companion and a parent's greatest ally. Designed by brilliant toy-company roboticist Gemma, M3GAN can listen and watch and learn as she becomes friend and teacher, playmate and protector, for the child she is bonded to. As Gemma faces pressure at work to deliver a finished version of M3GAN, she suddenly becomes the unprepared caretaker of her newly orphaned 8-year-old niece, Cady. Gemma decides to pair the M3GAN prototype with Cady in an attempt to resolve both problems—a decision that will have unimaginable consequences.