The final of Martino’s six gialli marked his transition to the burgeoning poliziottesci (police thriller) genre, reteamed him with prolific screenwriter Ernesto Gastaldi and launched his six-film collaboration with actor Claudio Cassinelli. Here Cassinelli is a cop who determines to bust a prostitution ring after the death of one of its conscripts, Patrizia Castaldi. Meanwhile her coworkers and Cassinelli’s’s potential witnesses are menaced by a serial killer. With Massimo Girotti (Ossessione) and Mel Ferrer.