Gemma, a roboticist at a toy company, uses artificial intelligence to develop M3GAN (short for Model 3 Generative Android), a lifelike doll programmed to be a child-s greatest companion and a parent-s greatest ally. After unexpectedly gaining custody of her niece Cady when the child-s parents die in a car accident, Gemma enlists the help of the M3GAN prototype, a decision that has horrific consequences when the doll becomes self-aware and overprotective of Cady, leading her to kill and harm anyone that gets in her way of |protecting| Cady and Gemma