About Mia Medina (Ang) has finally found the perfect subject for her PhD thesis film on Alzheimer's Disease. For the next several months, cameras will record the everyday life of mother Deborah Logan (Larson) and her daughter Sarah (Ramsay). But as the days progress, strange things begin to happen around Deborah that are not consistent with any findings about Alzheimer's. It becomes apparent that there's something besides Alzheimer's that has taken control of Deborah's life. It's an evil that is far worse than the debilitating disease with which she was first diagnosed.