The Outer Limits (1995)

Dr. Christina Markham and Sheriff Grady Markham live in small town America. Alzheimer's disease is slowly robbing Christina of her mother Helen, who lives in a nursing home along with her long time friend Gerry. When three apparently healthy young women age and die within hours, the Markhams are baffled and frightened. Grady interviews stunned witnesses and Christina seeks medical explanations, hoping to prevent another tragedy. Only after Helen and Gerry vanish is the astonishing answer to the puzzle finally revealed.