Part one is narrated by God, who in the voice of a somewhat snarky Brit, with occasional comments about the foibles and failings of the story's main characters, Eugene is a tale of Nigel Wellbourne, who engages in scientific inquiry to find and affect the genetic precursors of behavior and intellect, and in turn social order.
The story begins in early twentieth century Britain, with Nigel who, having failed early in his ministry career, marries and is then employed as a lab worker in the early eugenics movement. He succeeds at his first assignment, and is promoted to fieldwork, which he in time takes up in America. His wife has given birth first to a daughter of exceptional abilities, and later to a son with Mongolism.
Having seized upon a vague invitation to come to New York to work at the Cold Spring Harbor eugenics lab of Charles Davenport, Nigel quickly advances to lead a growing of field workers deployed to state mental institutions throughout the U. S. After his wife, dies, Wellbourne engages a coed to work first as a nanny and lab assistant.
His retarded son, Eugene, who has achieved a remarkable degree of social skill, notwithstanding his intellectual impairment, is seen alone in a barn with a young female, and owing to prohibitions of such comingling by defectives, he is soon sterilized. Depressed by what has happened, Eugene hangs himself. Overcome with grief and doubt, Nigel reflects on the consequences of the choices he has made. His research aid abruptly departs for her home in the East, and Nigel shortly thereafter leaves the state hospital for employment in California.
Part two of the book picks up with professor Ann Langley, who introduces her upper division course in behavioral genetics by recounting the history of the eugenics movement, then reveals a breakthrough in genetic engineering that now promises advances in treatment of hereditary maladies, as well as offering hope for improving human intelligence.
Meanwhile, Dr. Ann Langley learns through genealogical research that she is related to Nigel Wellbourne. Also troubled by the limited progress she has made in advancing her field, outraged by the direction of her Chinese collaborators who have begun unethical work in genetic engineering, and stressed by the challenges of teaching students imbued with contemporary cultural values, she opts to have a child through in vitro fertilization. Dr. Langley, who is 40 years old, after a lengthy and sometimes disheartening reproductive process, chooses implantation of an embryo she knows will have an outsized chance of being cognitively impaired. Notwithstanding the impact on her personal life and career, she ultimately gives birth to a child.
