Monsieur Durand-Bidon's mother-in-law is decidedly cantankerous. She never ceases - she who is a duchess - to reproach the latter for his low origins. One morning, at dawn, while he comes home "well watered", he is surprised with a comrade at the bottom of a bathtub. Taken for a homosexual, overwhelmed by Step-Mom, he will never stop trying to escape her and will end up, after many adventures, by learning a somewhat embarrassing secret about the pseudo-nobility of his step-family.