The Morals of Ruth Halbfass (1972)

Ruth is the wife of Erich Halbfass, a well-heeled corsetry manufacturer. Business is booming, Erich splashes around in the house swimming pool and daughter Aglaia attends school well. The bored middle-class wife begins a secret affair with Aglaia's drawing teacher Franz Vogelsang, setting murder and manslaughter in motion.