Georges and Anne are in their eighties. They are cultivated, retired music teachers. Their daughter, who is also a musician, lives abroad with her family. One day, Anne has a stroke, and the couple's bond of love is severely tested.

The Catholic Jean-Louis runs into an old friend, the Marxist Vidal, in Clermont-Ferrand around Christmas. Vidal introduces Jean-Louis to the modestly libertine, recently divorced Maud and the three engage in conversation on religion, atheism, love, morality and Blaise Pascal's life and writings on philosophy, faith and mathematics. Jean-Louis ends up spending a night at Maud's. Jean-Louis' Catholic views on marriage, fidelity and obligation make his situation a dilemma, as he has already, at the very beginning of the film, proclaimed his love for a young woman whom, however, he has never yet spoken to.