Mr. Lenz (Karel Höger), a German university professor escaped the country for Switzerland after the Nazis got to power. He settled in Zurich, established a books-and-paintings store, and married a young, pretty Evi (Jana Brejchová). Their calm life is disturbed by a visit of major general Strobach (Radovan Lukavský), an ex-school mate. Strobach hates Hitler and his regime and wants to fight against them. He brought Lenz a radio transmitter for his sending messages acquired from the Hitler general staff and Lenz is supposed to transmit them further to the particular stations and organizations.