The young violinist Fritz Molander inherited a Stradivarius, the so-called “star violin”, from his father, a famous conductor.
When Molander's concert agency demands a considerable advance payment, he is forced to sell his precious Stradivarius violin.
While she offers Holk to break off the engagement because of this "scandal", he wants to resign from this case as a public prosecutor in order not to get into a conflict of interest.
His investigation eventually reveals that the old instrument maker Dannemann had exchanged the star violin for a low-value but not immediately recognizable fake during a repair.
While Elisabeth can finally introduce her fiancé to her mother, the sounds coaxed from the Stradivarius by Fritz Molander ring out the open window.