The Rafferty's are immigrant Irish laborers living in Pittsburgh. Its patriarch, Patrick Rafferty, is wheelchair bound due to an industrial accident incurred at the Scott family steel mill. He blames the accident on working conditions at the mill and thus he hates the Scott's, despite who have more than adequately financially compensated Patrick. So Patrick is not too happy when his daughter Mary goes to work as a domestic in the Scott household. Despite Mary's lack of experience, she quickly becomes close friends with the entire family, which consists of parents William and Clarissa, and children William Jr., Paul, Ted and Constance. It is Paul from whom she attracts the most attention. The two fall in love. But Mary does not want to risk Paul's social standing and with the help of Clarissa decides to place some distance between herself and Paul. When William Sr. notices Paul's total obsession with work and the reason for Mary's departure, he decides Mary's return would be the best thing for Paul. After Mary's return, a strike occurs at the mill. Paul and Mary try to broker a deal between the Scott's and the workers, most of whom are friends of the Rafferty's. An undelivered communique results in tragic consequences. Despite still being in love, Paul and Mary realize a union between them is now impossible. Making other life choices - an especially unhappy one for Paul - Mary and Paul may still be able to eke out a life together due to a move by Clarissa, the move solely in an effort to ensure the continuation of the Scott name with the mill.