Without getting too detailed, here is the plot. Businessmen have been assembled on an island owned by George (Teodoro Corra). Also invited is an altruistic scientist, Fritz, who has discovered a new formula for an industrial resin. This discovery would be worth millions to the company who can produce it. The businessmen want to seduce Fritz to sell them the formula. Fritz wants to give the formula away at a conference in Geneva, so every company can benefit from it. Each of these businessmen brought their wife along. The wives are all nymphomaniacs, desiring sex with everyone who walks...including the other women. Oh yes, Isabel (Ely Galleani, see photo below) is the young daughter of George, and she appears to be a free-spirit with bizarre behavior. As Fritz rejects any offer for his formula, the murders start.
One by one, guests are stabbed or picked off by a sniper rifle. As bodies drop, lesbian trysts abound, and each wife engages in sexual activity out of their marital circle. The businessmen are more interested in obtaining Fritz' formula than they are surviving. As the corpses mount, and all communication with the outside world is cut off, the bodies are hung in a meat locker. Sweet, beautiful Isabel emerges as a suspect (at least for the viewer), but is that too easy? Every character comes across as ruthless, and the maxim "no one is innocent" prevails. The ending is both predictable, and a surprise.
Mario Bava didn't set out to create a morality tale, but here we have one. Those engaging in orgies and intimacy outside of marriage meet bloody fates. Is sweet Isabel actually a devious monster? Is one of our businessmen merely eliminating competition? Is jealousy at play, here? This is a good one, and available on Netflix. Next time you think of experimenting outside your current family unit, remeber the fate of many of the characters in "5 Dolls for an August Moon."