Gain tells two parallel stories: one, of Laura Bodey, divorced mother of two and successful real-estate agent in the small town of Lacewood, Illinois, who one day discovers that she has ovarian cancer; and two, of Clare Soap & Chemical, the company begun by three merchant brothers in 19th-century Boston, which by the turn of the century has grown into a large multiconglomerate with factories in Laura's hometown. As the history of Clare Soap changes through the history of America, so a modern-day Laura Bodey descends into a battle with her terminal illness.