A film adaptation of the opera by Jacques Offenbach. The stories upon which the opera is based are "Die Gesellschaft im Keller", "Der Sandmann" ("The Sandman", 1816), "Rath Krespel" ("Councillor Krespel", also known in English as "The Cremona Violin", 1818), and "Das verlorene Spiegelbild" ("The Lost Reflection") from "Die Abendteuer der Sylvester-Nacht" ("The Adventures of New Year's Eve", 1814). The "Chanson de Kleinzach" aria in the Prologue is based on the short story "Klein Zaches, genannt Zinnober" (1819).
I am not able to find the German original of “Councillor Krespel,” so I am basing this summary on English versions that appear on the websites of Virginia Commonwealth University and the University of Adelaide.
Councillor Krespel - Virginia Commonwealth University
Hans decided to discuss Krespel’s conduct with Professor Mueller. The professor said that Krespel was not insane. He pointed out that everyone had insane thoughts at times, but most people repressed them. In contrast, Councillor Krespel acted out his occasional insane thoughts, so that they were visible to everyone.