A mom in a nice suburban neighborhood earns the wrath of her new neighbor after saving the woman's foster daughter from a terrible accident, which causes the crazed neighbor to lose everything she cherishes.

Stephanie has a wonderful life in suburbia with a nice home, doting husband, and two daughters. Things couldn’t be better for her until a new family moves in across the street. Immediately, it becomes obvious that Nadia is a bad parent by not supervising her three young foster children. Stephanie’s husband Brian suggests she give them time to settle in before passing judgment on the new neighbors.

While Stephanie is gardening in front of her house, she spots young Molly, 18 months old, in nothing but a diaper playing out front alone. She chases a ball into the path of an oncoming car. Stephanie saves her but isn’t sure where she came from so she calls the police. The responding officer questions Nadia and finds out she belongs to her. Nadia pleads to sweep this under the rug or she may lose the foster kids and the money that comes with them but the officer reports it anyway.

Nadia blames Stephanie for losing her income. Nadia’s husband James wants her to get a job but she refuses so he leaves her. She has no money for living expenses and hits up her mom for help. Now holding a grudge against Stephanie for calling the police, she sets off on a quest to destroy her life. It starts with putting their full trash can back behind the house on trash day and escalates into hiring the older daughter to do some work for her just so she can get access to her house key and make copies, then entering their house and drugging juice in the refrigerator that makes Stephanie and the girls sick.

After killing the social worker for taking the kids from her, then James for leaving her high and dry, Nadia starts sending provocative messages to Brian’s phone from an unknown sender. Brian keeps this from Stephanie so she won’t take the messages seriously. Blocking the sender doesn’t work because Nadia buys numerous burner phones to harass him. Stephanie sees the messages one day and throws Brian out for cheating.

As bills pile up, desperation gets a strong foothold on the psychotic neighbor. Brian stops by to question her about the texts and is knocked out by Nadia. She then catches Karen and her little sister Megan when they get home from school and offer money for them to go with her and move some belongings. She drugs their drinks and drives them, along with an unconscious Brian, to a remote cottage she stumbled across.

In order to get Stephanie there, Nadia uses Karen’s phone to say the girls went to a friend’s house after school and need a ride home. Stephanie arrives at the cottage and receives a brick to the head. When she awakens, she finds Brian and the girls tied up. Nadia plans to take her family from her, which forces Stephanie to fight for their lives. During an altercation that ends up in the woods, Stephanie knocks out Nadia and reunites with her family.

New neighbors move in across the street, but Stephanie decides to play it safe by not interacting with them to soon.