Duet for Cannibals (1969)

Bauer, a university professor, and his wife, Francesca, hire someone to help in arranging some papers for publication. The employee, Tomas, comes to live with the couple, and quickly discovers that things are not quite right with them. Francesca and Tomas end up having sex while the professor goes after the young man’s mistress, Ingrid. Soon, the men swap partners, and reality and fantasy start to blur.