In an act of friendship and solidarity between two mining towns in 1929, the locals of Kriwoj Rog, Russia, give their flag as a gift to the locals of Bergstedt, Germany. This quickly takes on a symbolic meaning for the miners in Bergstedt as the Nazi party demands that this Soviet gesture be erased and the flag be replaced with their own. The miner and communist party functionary Otto Brosowski (Erwin Geschonneck) publicly declares it his duty to defend this flag against every danger, and he keeps his promise despite his family being threatened by torment and torture.

In November of 1939, the British consulate in Norway receives documents saying that the Nazis are conducting secret rocket research in Peenemünde. But the British doubt the authenticity of the so called "Oslo report". Thus, the Germans continue their experiments unimpeded. At the same time, resistance groups from France, England, Poland, and Germany try to find and to sabotage the secret Nazi research base. When the first "V 2" rocket is successfully launched, the Allied commanders finally become interested in the "Oslo report".