Linda Vargas (Montserrat Prous) works a showgirl number with Maria Toledano (Kali Hansa, The Night of the Sorcerers) before picking up Ortiz (Manuel Pereiro), seducing him, calling the cops and killing herself by slicing her own throat, which implicates him in her murder.
His wife, Rosa (Jacqueline Laurent) attempts to learn the truth and discovers from Countess Anna de Monterey (Anne Libert, The Demons, A Virgin Among the Living Dead) that her husband assaulted Linda when she was just a young girl, going from drugs to, well, the title is Sinner: The Secret Diary of a Nymphomaniac, so you can guess the rest.
Made after the death of Soledad Miranda and before Franco would fall for Lina Romay, this comes from the more serious side of Jess Franco, feeling like it was inspired by the structure of Citizen Kane, which makes sense more than the absolutely formless movies he’d make later in his career.
The worst thing is that Jacqueline Laurent was fired from her position as a drama teacher at a private high school because of this film. Her students learned that she had appeared nude in this film — made 39 years before — and the school’s administration claimed that this and other erotic thrillers made in the sixties and seventies posed a distraction.