Still mourning the death of her mother, 16-year-old Angela, who's had some behavioral and mental instability issues, strives to maintain harmony in the house. She takes care of her 6-year-old sister Chloe and tries to keep the peace with her difficult, goth 17-year-old sister Becca, who is furious that their father Jason pulled them out of school and hired grad student Gabby to homeschool them. When Becca starts exhibiting bizarre behavior, only Angela seems to notice that she is possessed by a dark and otherworldly force with plans to do something unspeakable to Chloe.