I.M. Mann, millionaire president of a large corporation, is known as "the man with the iron heart." James Boyd, cashier for Mann's corporation, is delayed one morning because of a dying mother, and is discharged. Then Boyd goes to Union headquarters with his story. The thousands of workmen employed by Mann finally reach the limit of endurance, and at a union meeting, resolve to demand increased wages, a cessation of child labor and other benefits, or strike. He refuses to hear a committee of workmen and says, "I'll close up the factories and let you starve." Boyd resolves to plead with Mrs. Mann for the workmen. He tells the wife, "Your husband holds the destiny of 50,000 people in his hands." Mann arrives at his palatial home at this moment. He is infuriated at the sight of Boyd. He strikes him and orders him thrown from the house. And then it is that Conscience appears to "the man with the iron heart." "Out of my heart forever, Conscience," exclaims Mann, but he is unable to stifle Conscience. Mrs. Mann leaves her stone-hearted husband, telling him that she will return when he resolves to grant the favors asked for by his workmen. Mann orders a strike breaker to fill his factories with non-union men by noon of tomorrow. At noon the following day, the union men march from the factories. They encounter the mob of strike breakers and a terrible conflict ensues in which the police are summoned, who with difficulty quell the rioters. Mann returns to his home and as he enters the threshold, he is shot by one of the rioters. Placed in his bed, Conscience appears before him in his delirium and also Death. He overcomes Death, but is unable to repulse Conscience. Conscience shows "the man with the iron heart" the scenes of suffering which he has caused, of his discharged cashier caring for the dying mother, the death of a little child, and of his wife pleading for leniency to the workmen. Overcome by Conscience, Mann is no longer known as "the man with the iron heart." He summons his wife to his bedside. He grants the request of his workmen and his reformation is complete.