Paranoia

A race-car driver, Carroll Baker as Helen, forms a bond with her ex-husband's new wife, Anna Proclemer as Constance Sauvage, at a plush villa, and their mutual dislike for her husband culminates into a plan to kill him. Their plot goes awry, leading to Constance's accidental death, which they then dispose of at sea. However, the victim's daughter, Marina Coffa as Mrs. Susan, arrives and suspects they murdered her mother, setting off a thrilling whodunit.