When a deadly mist engulfs Paris, people find refuge in the upper floors of the buildings. With no information, no electricity and hardly any supplies, Mathieu, Anna and their daughter Sarah try to survive the disaster.

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.

A group of young slackers spend most of their time hanging out in front of a Munich apartment building. When a Greek immigrant named Jorgos moves in, however, their aimless lives are shaken up. Soon new tensions arise both within the group and with Jorgos.