In the nineteen-sixties, in a civilized city in proper little Switzerland, a mysterious murder happens which takes twenty years to solve. The main characters are four old friends who meet regularly to play cards: Arnold Wiederkehr, detective; Franz Filbert, left-wing politician and journalist - the murder victim; Wilhelm Brauer, successful attorney; Arthur Stöckli, zoo keeper. Wiederkehr has taken early retirement and now lives in a remote village in southern Switzerland. In a comprehensive report for the prosecution he describes how he solved the Filbert case.