In an English mining town during the 1870s, Joan Lowrie falls in love with Fergus Derrick, the new chief engineer who vows to improve working conditions. Joan's father Don, however, runs the mine and likes conditions just as they are. As a result, he quickly learns to detest the crusading Fergus, even to the point of trying to murder him. Joan saves Fergus, after which Don is killed by one of the workers whom he habitually mistreated. Don's death removes the only impediment to Joan's romance as well as to improvements in the mine, so while Joan and Fergus make plans for their marriage, plans also are developed to make the mine safer and more efficient.