Two years after M3GAN's rampage, her creator, Gemma, resorts to resurrecting her infamous creation in order to take down Amelia, the military-grade weapon who was built by a defense contractor who stole M3GAN's underlying tech.

A brilliant toy company roboticist uses artificial intelligence to develop M3GAN, a life-like doll programmed to emotionally bond with her newly orphaned niece. But when the doll's programming works too well, she becomes overprotective of her new friend with terrifying results.