Having persuaded her resistant mother to send her to college, Kate Croft falls in love with science. Painfully rebuffed by a girl she longs for, and in flight from her own confusing sexuality, Kate finds refuge in the calm rationality of biology: its vision of a deeply interconnected world, and the promise that the new field of genetics can explain the way people are.
 
But science, too, turns out to be marred by human weakness. Despite her hard work and extraordinary gifts, Kate struggles, facing discrimination, competition, and scientific theft. At the same time, a love affair is threatened by Kate’s obsession with figuring out the meaning of the puzzling changes she sees in her experiments.