Devil in Ohio follows hospital psychiatrist Dr. Suzanne Mathis, who shelters a mysterious cult escapee, Mae. Her world is turned upside down as the strange girl's arrival threatens to tear her own family apart.

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.