Léa, the daughter of a wealthy Bordeaux family, is spending happy days at the Montillac family estate at the end of the 1930s. Radiant with youth, she charms all the men who meet her on the blue bicycle offered to her by her father. She is in deep love with Laurent, when she tells him, he lets her down. He is in love with Camille, Lea's best friend. The war sounds the death knell of her carelessness. She takes refuge in Paris. There, she finds Laurent, his secret love, who has just married Camille. During a party given him, she meets mysterious François -a friend of Laurent who works for the government. He goes right on and starts to win Lea's heart, but she is not interested. Laurent has to go to the front-line. He asks Lea to stay with Camille in Paris, to look after her and the unborn baby. But the German troops are progressing, and Léa and Camille are forced to leave the capital.