The wealthy Frenchman Raoul lives with his mother and his cousin Therese in a magnificent villa on the Riviera. Therese is deeply in love with her relative, but he seems to reciprocate only "brotherly" affection. One day, a visitor arrives: the lustful Lydia, a friend of Therese's, known as a man-eating and amoral woman. It isn't long before Raoul, the master of the house, falls completely under the spell of the blonde siren from abroad, and the two become engaged and eventually married.