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.

Crippled by loneliness, a woman is prescribed a drug that gives her an imaginary friend. But this new relationship becomes more complicated than she could ever have imagined.