The July 1958 vacation, on a beach on the Atlantic coast. Little Sophie, 8 years old, and her big sister Frédérique suffer from the bad understanding between their parents, presenting the drama of divorce which will not fail to occur.

Summer 1958. Frédérique and Sophie go on vacation as they do every year to La Baule, where they find their uncle, Léon, nice and loud mouth, their aunt Bella, pregnant, and their little cousins. Like every year? Not quite. This year, Léna, their mother, is still staying in Lyon for mysterious reasons. If Sophie's six-year-old's don't pay attention any more, Frédérique's thirteen-year-old noticed a discomfort between Mom and Dad. In fact, nothing is going well. Léna can no longer support life with Michel, her husband, and is in love with a young artist, Jean-Claude. He comes to join Léna as soon as she arrives and finds her every evening on the beach, in her tent. The smoldering crisis does not prevent children from doing stupid things (setting fire to the Mickey Club, poisoning goldfish with suppositories), nor from experiencing their first emotional emotions. One day, Michel arrives. Things are going very badly, and Frédérique is forced to intervene to separate him from his mother. Lena then announces her decision to divorce the children. Michel will try to convince her one last time, but in vain. At the end of the holidays, Léna and the two little girls do not return to Lyon.