Two years after M3GAN, a marvel of artificial intelligence, went rogue and embarked on a murderous (and impeccably choreographed) 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.