"She's not just a toy, she's part of the family." Megan (M3GAN) is a lifelike toy doll with a high degree of artificial intelligence, designed to be the best playmate for children and the most reassuring ally for parents. This toy doll is carefully designed by Gemma (Allison Williams), an outstanding robotics expert at a toy company. Megan can learn human behavior by listening and observing, and become a friend, teacher, playmate and protector of the children she takes care of. When Gemma suddenly becomes the guardian of her eight-year-old niece Katie (Violet McGraw), who lost her parents, Gemma is not sure or ready to be a good parent. In addition, her work pressure is very huge, so she decides to pair the artificial intelligence toy doll Megan and Katie, trying to solve the two problems of taking care of Katie, an orphan, and relieving her work pressure, but her decision has unimaginable serious consequences.