This film is rather unusual for a giallo. It's well-filmed but not particularly stylized. The plot is rather strange, but generally makes sense. It has no graphic violence, and although it has plenty of perverse sexual situations, it barely has even the circumspect nudity of the earliest Caroll Baker gialli ("Sweet Body of Deborah", "Orgasmo", etc.). A society woman (played by Dagmar Lassender) is nearly raped on the beach by a sinister man who tells her that her industrialist husband has murdered one of his colleagues. The man blackmails her into sleeping with him by threatening to expose her husband, and then blackmails her again with graphic photos of their affair. The husband meanwhile is himself involved with her sexually voracious best friend (played by Nieves Navarro aka Susan Scott), and the whole thing might be some kind of plot to drive her mad.
This movie works mainly because of the acting. Dagmar Lassander was one of the better actresses to appear in gialli, second only to Edwige Fenech and the aforementioned Carroll Baker at playing these hysterical, beleaguered victim roles. Even better is Nieves Navarro as her sex-hungry best friend who has pornographic pictures taken of herself and says at one point, after Lassender's character confides about her near rape, that she would have "adored being violated" (there's a kind of refreshingly politically incorrectness to the ridiculous dubbed dialogue of these movies). She is such a dubious and ambiguous character that even at the end it is not clear whether she is a loyal friend to the protagonist or an unexposed villain.
The director, Luciano Ercoli, is the Italian husband of former Spanish model Navarro. He made several other gialli, all featuring his wife, but this is probably the one where he made the best use of her. He is no Dario Argento or even Sergio Martino, but his direction is certainly adequate. The screenwriter, Ernesto Gastaldi, contributed scripts for any number of these pictures and he puts forth a pretty decent and suspenseful one here. This movie is kind of hard to find right now, but it is worth seeing if you like these kind of movies.