The film is from the point of view of a man remembering when he was a boy who isn't very athletic, but whose mother and father are. As a boy, he imagines he has a brother Simon who is as athletic as he himself is not. In his early teens, the neighbor (played by Julie Depardieu, Gerarad's daughter) tells him the truth where he learns his mother is not his father's first wife and his father had a son Simon by his first wife who was very athletic. It might sound like I'm giving the plot away, but this is not the "secret" of the title. The secret of the title is what happened to the family and friends during World War II. It's a very good movie and I recommend it. It's not a comedy, but a drama with a serious plot.