It's tempting to look at this movie and think: What on earth is Carroll Baker doing in this piece of junk? (One becomes a lot less judgmental after reading Baker's autobiography and finding out this film came along at a time when Baker was in somewhat dire financial straits.)
It's still a piece of junk. "Paranoia" is a nasty, amateurish, inept thriller that tries hard to be sexy, but is more embarrassing than erotic. I don't know how it plays in Italian, but the (partly dubbed) English dialogue is as ghastly as the direction (somebody take away Umberto Lenzi's zoom lens!). There is one intriguing, identity-blurring moment when Baker playfully dons a dark wig that makes her look so much like co-star Colette Descombes, it's spooky. (Yes, of course it's a rip-off of "L'Avventura," but in this film, you take whatever you can get.) The movie's ending is beneath "Contempt."
(Interestingly, Baker in her memoirs mistakenly identifies her character as a divorcée instead of a widow, and never mentions the movie by name, either by its American title, "Paranoia," or its oh-so-charming Italian appellation, "Orgasmo.")