When a woman becomes obsessed with her new grandson, she threatens to destroy her family in her quest to be the grandma she is determined to become.

Judy, the only child of Katherine and Walter, is married to Philip, a Navy man. They live a few states away from their family. At Christmas via Skype, Judy reveals that she is three months pregnant with a boy. While the news is bliss for Katherine, finding out that Philip’s parents were told first leaves her bitter.

Katherine insists that Judy calls her the moment she goes into labor so Walter and she can fly there in time for the birth. Judy decides to share the special time with Philip only. After Carson arrives, Judy Skypes Katherine to let her see her grandson. As before, Katherine feels both happiness and anger at a special situation. She was left out of the birth of her first grandchild, something she struggles to get past.

But there’s hope on her part that with a new baby and Philip being discharged from the navy soon that they will move back to Cincinnati. Philip’s family lives an hour away from Katherine’s home so it would be best for both sides of the family, and they could help with the baby.

Katherine and Walter visit Judy. They discover that the couple recently bought a house and plan to stay there. When Judy gets a call that Philip has been in a car accident, she wonders what she would do without him on her own. Katherine assures her that Carson and she would move home so family could help her. Judy agrees with the plan. To Katherine’s dismay, Philip recovers. When Katherine and Walter arrive home, Katherine now feels alone. Recalling her conversation with Judy about Philip’s potential demise, a plan brews in her demented head.

Claiming she is going on a weekend trip with co-workers, Katherine rents a car under her maiden name and takes off for Judy’s house. There, she watches Philip. When he takes a thermos into a civilian job interview, she slips fentanyl into his drink. Philip dies in his car soon after drinking it. While Katherine acts devastated at the news, she helps to move Judy and the baby back home where she feels they belong.

When Walter’s sister offers Judy a job, Katherine kills her to prevent Judy from getting childcare for her son. Then Walter finds out what his wife has done and dies due to a tragic accident. Judy eventually gets a job and finds daycare for Carson. On the first day, Katherine picks him up and is unhappy with the place. She takes a leave from work to watch him herself. Then she decides he needs his mom and gets Judy fired.

When Judy puts 2 and 2 together, she figures out what her mom has done and is ready to leave when Katherine knocks her out. Judy awakens inside a remote cottage Katherine has rented in the middle of nowhere. Her only hope of escape with an infant in extreme heat is to find the keys for Katherine’s car. She locates them and tries to flee, but Katherine fights to stop her. Judy wins the battle and sees her mom taken to prison, where she grows delusional about the failed relationship she has with her remaining family.