Colonel Maratka and Major Kalasz, employees of the Czechoslovakian defense forces, are facing a difficult task. They must complete a mission that is important for the security of their country. The Prague headquarters of the state security service had previously received information from the GDR that West German military intelligence had apparently succeeded in deciphering the secret code B/13 used in the field of missile armament.

On the run from police in America, Antonio Morena, a former World War II aviator and black-marketeer, finds himself in South America working for the all-powerful United Fruit Company, known to the natives as "the Green Monster".

Railway employee Fritz Marr is not regarded well by his superiors. It is the year 1920, and trains regularly pass the railway hub of Erfurt to the East to secretly transport weapons for the fight against the young Soviet Union. Marr knows about this and wants to mobilise other workers to stop these illegal deliveries. To muzzle him, Marr is relocated to a remote rail work construction site.