Oedipus Orca is the sequel to La Orca both directed by Visconti and starring Rena Niehaus. In La Orca a high school aged girl played by Niehaus is kidnapped and held for ransom, while the second movie Oedipus Orca is about her life with her family and boyfriend after she returns home. The first film was somewhat controversial and labeled pornographic by some due to its exploitive nudity and sexuality involving a teenage girl (Rena is rumoured to have actually been 21 or 22 at the time). The first movie is actually pretty good with a great ending, while the second is less focused and sometimes seems like it was done purely as an exploitive film. SPOILER ALERT!, From here on.
La Orca is largely about the girl's relationship with her kidnappers. One of them sexually molests her in a fairly explicit scene. After that she uses sex with him as a way to gain favors and eventually ends up controlling the relationship. She has her revenge at the end a moment before the police arrive to rescue her.
Oedipus Orca begins with her return home. The exploitive side as the film series continues as she is nude every few minutes. She once again uses sex to her advantage against a family friend. This movie has lots of flashbacks to the first film and deals with her emotional state a lot. The most memorable is when she visits the room she was held captive in and masturbates while recalling having sex with her captor. It makes as strong a statement as I can think of, of how the mind can be twisted by such a situation. - xrayrandy, IMDb