Die Katze im Sack (1965)

Vic Malloy discovers the letter of a girl in his letter tray. The shnodder detective has probably forgotten to open it some time ago. He now learns that the young millionaire should have come to life immediately after sending the letter. But who inherited the fortune? The sister who says in the letter that she should be in the violence of blackmailers. With his detective colleague Jack, Vic goes after the matter. They encounter a secret crime.