Anton Ivanovich Voronov is a highly respected professor at the Moscow Conservatoire, who places the music of Bach above everything else and regards it as the ultimate yardstick by which other musical accomplishments must be measured. His daughter, Serafima, is an aspiring singer with great potential, and her father’s anger is aroused when she begins singing in the operetta composed by Aleksei Mukhin, thus abandoning what he considers the higher calling of opera. Mukhin’s work, however, demands a high level of ability from his soloist, and Anton Ivanovich is persuaded of the legitimacy of operetta as a musical genre when, in a dream, he is visited by Johann Sebastian Bach himself, who tells him that ‘people need all kinds of music’.

The eve of the 1905 Russian revolution was unquiet at the Skrobotova and Bardin factory. In response to the fair demand of the workers to dismiss the cruel and rude master, the masters close the factory and call in the troops. They shoot of one of the workers, who failed to restrain a rush of hatred towards the owners, ending Skrobotov's life. Gendarmes arrive at the factory. They succeed in uncovering the social democratic organization in the factory. The arrested workers oppose hysterical cruelty of gendarmes with calm, confident courage.