Antonio Berlinghieri (Ugo Tognazzi) is a 39-year-old engineer travelling on a highway one summer in his sports car when he sees a broken-down car with a group of teenagers. He stops to try to help them but soon discovers that the young men have a frivolous attitude. At first he thinks of leaving to continue his trip but then notices the beauty of Francesca (Catherine Spaak), a girl half his age. He decides to remain with the group even if the different ages causes some troubles.