When 15-year-old Jules Mathis comes home from school to find a strange girl sitting in her kitchen, her psychiatrist mother reveals that Mae is one of her patients at the hospital and will be staying with their family for a few days. But soon Mae is wearing Jules' clothes, sleeping in her bedroom, edging her out of her position on the school paper, and flirting with Jules' crush. And Mae has no intention of leaving.
Then things get weird.
Jules walks in on a half-dressed Mae, startled to see a pentagram carved into Mae's back. Jules pieces together clues and discovers that Mae is a survivor of the strange cult that's embedded in a nearby town. And the cult will stop at nothing to get Mae back.