When Gemma is forced out of the blue to become the legal guardian of Cady, her orphaned eight-year-old niece, she in turn suffers a shock, not sure she has what it takes to become a parent overnight. Under intense pressure at work, Gemma decides to team up her prototype doll, M3GAN, with Cady in an attempt to solve both of their problems – but this decision will prove to be extraordinarily dramatic and have some unimaginable consequences. .