Rudolf Bartoš, the owner of a farm, quarry and factory, is extremely rich, however, he is unapproachable and irritable, and the dread of his employees. One day he falls down a steep slope by a river and hurts himself. The quarryman Fábera finds him groaning in pain and takes him to his cottage.

The story of young boys who have proven their loyalty to the republic unfolds in the setting of a boarding school for miners' apprentices. A tunnel is dug from the Engels mine to the Ludvik mine, so that the two mines can be connected to form the Engels mine. However, the project is targeted by subversives who want to flood it, regardless of human lives.