10-year-old Cady, along with her parents, is involved in a car accident. Her parents die, and Cady is taken in by her aunt Gemma, who works for a technology-based toy company. Unsure how to handle the sudden responsibility and reluctant to spend time with her niece, Gemma introduces Cady to M3gan, an experimental android doll with artificial intelligence. M3gan's primary goal is to protect Cady from any physical or emotional harm, and she takes this responsibility very seriously.