NOVA explores the legacy of one of history's most infamous disease carriers: Mary Mallon, aka "Typhoid Mary."

Interweaving biography and social history, this episode tells the extraordinary story of Mary Mallon, better known as Typhoid Mary. She gained this notoriety by being the first person in North America to be identified as a healthy carrier of typhoid fever. Despite her indignant protests of innocence, she was incarcerated for years on an island in the East River. Mary Mallon's saga throws into vivid relief the emerging science of public health, and the social, ethical and legal dilemmas it posed to its pioneers at the turn of the 20th century.