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.
Jaroslav Průcha
František Peterka
Jarmila Krulišová
Oldřich Lukeš
Vladimír Hlavatý
