Léonard Monestier has made his fortune trading on the stock exchange. His eccentric wife Cynthia almost bankrupts him by selling some of his shares to buy an oil concession in South America. Convinced that the concession is a fake, Monestier decides to sell it on to a friend of the family, the naive millionaire Antoine Brévin. Antoine wants to marry his daughter, Patricia. However, Patricia has a different opinion on the matter. She manages to persuade the car delivery guy, Simon Guilbaud, to pretend to be her husband. Unaware of this development, Monestier invites Antoine to his house in order to get him to agree to buy the oil concession. After the invitation to Antoine, the butler Charles informs Monestier of the rushed marriage of Patricia. To prove that the concession is genuine, Monestier hires his son-in-law Simon to pretend to be his son, Paul, who is currently in South America. At this point, the real Paul turns up, with a Latin showgirl, Palma. Monestier has to resort to ever more desperate schemes to get Antoine to sign his cheque.