A bishop asks the Mozart family, now on a concert tour, to take a valuable violin to Munich as a present for the prince-elector. As always, Devilius wants to get the Mozarts into trouble, so he replaces the valuable violin with a worthless old fiddle. He hopes to make it look like the Mozarts sold the valuable violin in order to make money. Then, Devilius will simply hand over the real violin and receive generous praise.