Jindřich Tůma, a partner in the gas mask shop "Asana", has a very energetic wife who promotes a vegetarian diet. The real soul of the company is Ing. Ivan Kareš, who also leads civil defense exercises. On the street, during a practice air raid warning, he sternly reprimands a girl who did not go to shelter. It is Věrka, the Tůma's niece, who comes from the countryside to finish her studies in Prague. Věrka enters the seventh grade and soon shares the enthusiasm of her classmates for an unknown composer whose pseudonym is Michal Marhan. Ing. Kareš gives a lecture on civil defense in the seventh grade and so meets Věrka again. Kareš tries to convince the girls of the necessity of more concrete life ideals. At the premiere of Marhan's operetta "Píseň o štěstí" it turns out that Kareš is the composer. The girls give him a standing ovation. Ivan ignores Věrka, with whom he has recently had a falling out. The stubborn girl therefore leaves for home...