Mary Rafferty comes from a poor family of steel mill workers in 19th Century Pittsburgh. Her family objects when she goes to work as a maid for the wealthy Scott family which controls the mill. Mary catches the attention of handsome scion Paul Scott, but their romance is complicated by Paul's engagement to someone else and a bitter strike among the mill workers.

Set in the Soviet Union in the 70's. The plot is based on real industrial conflicts in the life of the country's largest metallurgical plant, where there are many acute problems. Modernization of Soviet metallurgical industry causes a clash between old style Communist bosses and the new generation of engineers and managers.