Pierre Lachenay, a middle-aged, well-known publisher and lecturer, is married to Franca, an unbalanced woman, and father of Sabine, a 10-year-old girl. While traveling to Lisbon for a lecture, Pierre Lachenay has a one night stand with Nicole, the Panair do Brasil air stewardess. He wants to see her again and again, they travel to Reims together, and Pierre hides the affair from his family, mostly to spare his daughter the anguish of a separation. Nicole is taking it lightly but Pierre, misunderstanding her feelings and expectations, decides to live with her. The couple's break-up leads to a tragic end.