This quite rare movie by Sergio Martino is an odd thing. As the title presumes, it starts off like a typical giallo: A man with sunglasses stalks and slashes a young woman. But after the murder, the movie becomes a film in style of the "poliziescho", the Italian crime movie of the 1970s, as the audience follows an undercover cop searching for the killer and also for the kidnappers of a young boy (but the audience doesn't know for a long time either that the cop really is one and that the murder case and the kidnapping rely to each other). All this culminates (within the first half of the movie) in a car chase which offers enough gags to make the scene pure slapstick.After that, the giallo style returns as the sunglassed killer goes on a killing spree. The crime movie is back as the plot unfolds to have its motive in mob-style drug dealing. And let's not forget: The killings have also to do with professional child prostitution and abuse. A really wild mix, even more so if one considers that the film sometimes boosts cheap (if mostly funny) humor.The cool sound track is reminiscent of the early scores by "Goblin" for Dario Argento's films, and it seems that Ernesto Gastaldi, who wrote the story and co-wrote the screenplay with director Martino, was influenced by Massimo Dallamano's great "La Polizia Chiede Aiuto" that was made one year earlier.All in all, this surely is not Martino's best film (his "pure" gialli are more enjoyable), but if one gets used to the unusual concoction of such different topics and styles, it's an entertaining and sometimes hilariously funny, fast paced and thrilling movie that even boosts some harsh social comment.imdb comment