New York City, 1906 - a deadly outbreak of typhoid fever is sweeping the city. Sixteen-year-old budding scientist Prudence Galewski leaves secretarial school to follow her dreams and work as an assistant in the Department of Health and Sanitation. This agency is responsible for discovering the reason for the spread of the deadly disease. Meet 'Typhoid Mary' the Irish immigrant blamed for this outbreak, who has never been sick a day in her life. Follow the path of Prudence and her boss, the head epidemiologist as they try to prove what no one else will believe - that someone without symtoms can be the carrier.
This historical fiction is told in journal form and very satisfyingly chronicles the heroine's growth as a person as well as a scientist in the turbulent era when women did not even have the right to vote.