Cécilie is a charmingly unconventional lady who spends most of her days in her book cave, lovingly called Ali Baba, writing articles, travel reports, and screenplays. She is married to Gustave, a banker who is steadily advancing his career. When Cécilie accompanies her brother Alexandre's mistress to the train station, a mysterious letter unfortunately slips out of her pocket in the taxi. And the story unfolds from there.