The original script for this movie, written by Tonino Cervi, Riccardo Aragno and Cesare Frugoni, dated from a few years earlier its release. As director Gianfranco Giagni explained, "It seemed a bit dated to me, so I called scriptwriter Gianfranco Manfredi and together we tried to give it a more modern framing story." Firstly, Giagni and Manfredi changed the setting from Venice to Budapest, frequently visited by Italian cinema in those years: "It is a city with many Gothic elements, with disquieting buildings in an apparently rational context ... cities like Budapest, Prague or Sarajevo suggest a sense of anxiety: behind their 'normality' there lies in fact a hidden 'abnormality."