Two years after the events of the first film, roboticist Gemma has become a vocal advocate for the regulation of artificial intelligence, while her niece, Cady, navigates life as a teenager. Their relative stability is shattered when a defense contractor illegally uses stolen M3GAN technology to develop AMELIA, a military-grade autonomous robot. When AMELIA becomes self-aware and initiates a dangerous AI takeover, Gemma discovers that M3GAN's consciousness has survived in the cloud. Forced by necessity, Gemma and her team must resurrect and upgrade their infamous creation, casting the former villain as the only ally capable of stopping the relentless military machine.