Three Women in a Bonfire (1979)

Alex, a real estate businessman, has no concerns in giving her wife every kind of freedom. They invite Gloria, an old friend of both, to spend the summer break in their countryside house next to the beach. Gloria doesn't come alone: she comes with young Susy, her lover. Alex will use all of his charms and luxury to manipulate his new guests; meanwhile, his wife and Gloria will gang up to murder him.