Latina novelist Alma Huebner is suffering from writer's block and is years past the completion date for yet another of her bestselling family sagas. Her husband, Richard, works for a humanitarian organization dedicated to the health and prosperity of developing countries and wants her help on an extended AIDS assignment in the Dominican Republic. But Alma begs off joining him: the publisher is breathing down her neck. She promises to work hard and follow him a bit later.

The truth is that Alma is seriously sidetracked by a story she has stumbled across. It's the story of a much earlier medical do-gooder, Spaniard Francisco Xavier Balmis, who in 1803 undertook to vaccinate the populations of Spain's American colonies against smallpox. To do this, he required live "carriers" of the vaccine.

Of greater interest to Alma is Isabel Sendales y Gómez, director of La Casa de Expósitos, who was asked to select twenty-two orphan boys to be the vaccine carriers. She agreed— with the stipulation that she would accompany the boys on the proposed two-year voyage. Her strength and courage inspire Alma, who finds herself becoming obsessed with the details of Isabel's adventures.

This resplendent novel-within-a-novel spins the disparate tales of two remarkable women, both of whom are swept along by machismo. In depicting their confrontation of the great scourges of their respective eras, Alvarez exposes the conflict between altruism and ambition.