A wealthy man has two sons,one of them is legitimate,the other is not.The first offspring has had a life of luxury and he has become a lazy good for nothing whereas the youthful indiscretion has turned into an artist.He is nicknamed "Gringalet" .Now his father wants him to meet his half-brother ,his mother-in-law and the rest of the family. Gringalet will turn this bourgeois family upside down:they become nice,the big brother becoming a perfect businessman who stops scouring nightclubs to spend most of his time with his fiancee Josette.There's the rub,cause Gringalet is also in love with her.