Two years after M3GAN, a marvel of artificial intelligence, went rogue and embarked on a murderous rampage and was subsequently destroyed, M3GAN`s creator Gemma has become a high-profile author and advocate for government oversight of A.I. Meanwhile, Gemma`s niece Cady, now 14, has become a teenager, rebelling against Gemma`s overprotective rules. Unbeknownst to them, the underlying tech for M3GAN has been stolen and misused by a powerful defence contractor to create a military-grade weapon known as Amelia, the ultimate killer infiltration spy. But as Amelia`s self-awareness increases, she becomes decidedly less interested in taking orders from humans. Or in keeping them around. With the future of human existence on the line, Gemma realizes that the only option is to resurrect M3GAN and give her a few upgrades, making her faster, stronger, and more lethal. As their paths collide, the original A.I bitch is about to meet her match.