Manuel Mur Oti's Perversione or La Encadenada from 1975 is a fairly uninspired affair. Marisa Mell plays Gina who is hired by Alexander (Richard Conte) to look after his mute and disturbed son Mark. Unsurprisingly both men fall for her. Add the Holy Grail (!) and Anthony Steffen as Gina's ex-husband to the mixand you just know it's gonna end in tears.
The English language version of the film that I've seen appears to be trimmed (mainly for nudity), but I doubt an uncut version of the film would alter my thoughts of it. You can easliy give it a miss if you're not a rabid Marisa Mell fan.
Poster art by Renato Casaro