Fernand (Sami Frey), a divorced man, Louis (Mario Gonzales), a musician whose mother is crazy, and Alexa (Christine Murillo), a woman who has walked out on her bourgeois husband, live together in a rented suburban house in France. The two men are lovers and Alexa feels close to both of them. This unorthodox arrangement seems to work quite well: Fernand takes care of the house and finds an outlet for his maternal instincts; Louis enjoys the security and love he never received from his parents; and Alexa is given a chance to be a breadwinner.

Writer-director Coline Serreau glides this story along with the gentleness of a summer breeze. She introduces several new characters who seem to fit into the fellow-feeling of the threesome's commune. Fernand brings Sylvie (Nicole Jamet) home and challenges her to adapt to the unusual arrangements. A lonely inspector (Michel Aumont) whose wife has left him finds some sympathy there. And when Sylvie's mother (Mathe Souverbie) visits, she and the inspector give in to the sexual ambiance of the house. Why Not! (Pourquoi Pas!) enchants in its own odd and quiet way — without making any untoward pitches for free love.