Sam Dalmas (Tony Musante, We Own the Night), an American writer living in Rome, inadvertently witnesses a brutal attack on a woman (Eva Renzi, Funeral in Berlin) in a modern art gallery. Powerless to help, he grows increasingly obsessed with the incident. Convinced that something he saw that night holds the key to identifying the maniac terrorizing Rome, he launches his own investigation parallel to that of the police, heedless of the danger to both himself and his girlfriend Giulia (Suzy Kendall, Spasmo).