Five Dolls for an August Moon

Five Dolls for an August Moon Italianbambole per la luna dagosto is a 1970 Italian giallo film directed by Mario Bava. It concerns a group of people who have gathered on a remote island for fun and relaxation. One of the guests is a chemist who has created a revolutionary new chemical process, and several of the attending industrialists are eager to buy it from him. Business problems become moot when someone begins killing off the attendees one by one.

Farrell is immediately established as a decent man, and although his marriage to his wife, Trudy Ira von Frstenberg, appears to be content, she is actually involved in a secret romance with Starks artist wife Jill Edith Meloni. Starks business partner, Nick Maurice Poli, is verbally abusive to his coquettish wife Marie Edwige Fenech, but does not object to her sleeping with other men, one of whom is the houseboy and manservant Charles Mauro Bosco. Stark is less of a husband to Jill than he is a business manager. He arranges for her to have her paintings and artwork publicly displayed and is also a source of constant criticism. The sole happy couple appears to be Nicks coworker Jack Renato Rossini and his wife Peggy Helene Ronee. Also among the guests is Isabelle Justine Gall, a teenage girl who is in Starks care while her parents are away.As Stark, Nick, and Jack badger Farrell for the secret of the formula by offering himmillion each from their Swiss bank accounts, Jill discovers the dead body of Charles on the beach. Having already sent the motor launch away to prevent Farrell from leaving the island, and with the radio out of commission, Stark has no way of contacting the mainland. So, Charles body is moved into a large walkin freezer where it hangs with other chunks of meat. ........

Source: Wikipedia