The Investigation (1965) is TV version of a play by German playwright Peter Weiss that depicts the Frankfurt Auschwitz Trials of 1963–1965.

Wassa Schelesnowa, a manipulative matriarch who will stop at nothing to keep her business afloat and her family together. Infanticide, forgery, murder, blackmail, adultery, exile, and plain old-fashioned greed are the order of the day as Wassa's colorful clan tries to scheme its way out of the house and into financial independence.

Berlin's theatre crowd is excited about the new operetta "Frau Luna". But for the head of the city's vice police, who was invited to the dress rehearsal, the costumes for the ladies onstage are a bit too revealing. He demands the show be cancelled as offensive. The president of the Thusneldenbund has taken it upon himself to alert everyone about the growth of immorality in the capital. The theatre director Knopp has come up with an idea to convince these "fine" gentlemen to let the operetta go onstage again: He intends to win over the friendship of the moral police and then nothing will stand in the way of "Frau Luna" once more being performed.