Linda has a seemingly-perfect marriage with her rugged and handsome husband Mark, and they have an adorable 8-year-old daughter, Chloe. But when Chloe is injured by an elderly babysitter who has slipped into dementia, Linda wants to ensure that her child is never hurt again. Heather, the new babysitter, initially seems like the ideal addition to this practically-perfect family, but she's actually a schemer who exploits the cracks in Linda and Mark's relationship--and her intentions go far beyond the mischievous.