In a clash between science and civil rights, the protection of citizens' health trumps legalities when Mary Mallon is identified as a carrier of typhoid fever. An Irish immigrant and gifted cook, Mary has found employment with notable New York families. She makes a good wage and lives with her lover, Alfred Briehof, until she is abruptly swept from her position by authorities and held in isolation in a cottage on North Brother Island in the East River, site of a tubercular hospital. Labeled "an asymptomatic carrier" of typhoid fever in 1907 and denied benefit of legal counsel, Mary is spirited away for four years before she is released.

Mary, a scrapper who has made her way through hard work and ingenuity since coming to New York in 1886, chafes at the injustice of her predicament, inspiring sympathy from supporters who don't believe the charges against her. Even Mary cannot get her head around the suggestion that she is responsible for the deaths of twenty-three people. Though the science is explained, medical jargon is impossible for an uneducated woman to navigate, resulting in her denial and years of rationalization rather than acceptance or acknowledgement. Mary rages at the decision by authorities that has separated her from her lover and her friends in New York City, worries when Alfred's letters grow more scarce over time.

Keane's novel is successful because it is constructed in factual events but portrays the drama from Mary's perspective. Shamed by the sobriquet "Typhoid Mary" that shadows her even after her release, she is victimized by a zealous physician too embroiled in that conflict to consider any validity to his claim that she is a carrier of the disease. By its nature, the disease is selective enough that Mary is able to validate her own opinion and blind herself to the danger she presents to the public. She is punished for actions she does not believe are founded on truth, harassed by a physician who is both fanatical and merciless when confronting the woman he assumes is the sole source of contamination. (She's not.)

In the early 20th century, New York is a cauldron of industry, a confluence of humanity drawn to economic opportunity. Immigrants flock to a city unprepared for the social ills that will arise—the spread of poverty, tenements seething with families willing to sacrifice for their children, to compete, to survive. This very mentality, ambition and hard work to achieve success, drives Mary, her days too short and too busy to allow time for consideration, science literally counterintuitive to her way of life. Hence the denial that exacerbates her situation.

Keane is most inspired when inhabiting Mary's inner thoughts, her victimization, rationalization and determination not to be extinguished as a person. Her love affair with Alfred becomes collateral damage to her incarceration and subsequent employment as a laundress, a step lower on the ladder she has so rigorously climbed. The few thoughts that rise to the surface of her conscience are quickly pushed aside as Mary is once more seduced by a job where she will be cooking for the public, this time at a prestigious maternity hospital, forgetful in her joy of the careless taste, the spoon stuck back in the bowl, the spread of sickness and the face of her old nemesis waiting with a battalion of policemen to remind her of a broken promise.

It should be said in Mary's defense that once she realizes that someone she has cooked for has lost a loved one, she is appropriately chastened, willing to accept responsibility for her actions, cementing her history in New York as the infamous "Typhoid Mary."