Erich Kubak is an excavator operator at the lignite plant. A technical weakness in the excavator, which repeatedly leads to production downtime, is causing problems for everyone. Erich works on an improvement, but this is not accepted by the chief engineer. On his own initiative, Erich carries out an experiment and causes a great deal of damage. He is dismissed as excavator operator and then resigns. Meanwhile, his son Ewald, who also works at the plant, manages to interest the chief engineer in his father's improvement proposal. Together they work on perfecting it. When Erich finds out about this, he returns to the factory.