Prolific Italian filmmaker Duccio Tessari (La Morte Risale a Ieri Sera) returned to the giallo field with this first-rate detective thriller which begins with a French co-ed (Carole Andre) repeatedly stabbed in a park during a thunderstorm. The suspicion falls on sportscaster Alessandro Marchi (Giancarlo Sbargia), who is being framed (or so it seems) by his trysting wife (Ida Galli, aka Evelyn Stewart) and lawyer (Gunther M. Stoll). Unfortunately, while Marchi is being railroaded into prison, the murders begin anew, and Marchi is released to face the dead girl's grieving lover (Helmut Berger), whose motives would later be echoed in even better Italian thrillers such as Tenebre.