At the beginning of this crime story, the focus is on Mrs. Wilde's fiftieth birthday. Her three daughters, Lissi, Monika, and Carmen, had conspired to make this day special. The still single sisters, Monika and Carmen, wanted to combine the pleasant with the useful by introducing their parents to their friends. The oldest daughter, who was already married, had studied law and was now a prosecutor in Frankfurt. However, just at the peak of the birthday celebration, something unforeseen happens. Misfortune begins to unfold. A poisoning and a murder take the events in a completely different direction. A special commission is established by the state criminal police, led by Chief Inspector Ferdinand Köstel, also respectfully known as "The Fox." At that time, no one could have guessed the direction in which the events would unfold.