Charles Dréant has compromising files on politicians. The Guenn, member of a party, seeks to recover them.

The tiercé is, in France, a very popular game linked to horse racing. It's a game where you have to reckon with chance, but not for everyone. Some people know that we pay jockeys to keep horses and even know those who pay them. Pierre Chazerand (Michel Piccoli) and Charles Dréant (Michel Galabru) are among them. Chazerand is even the black beast of the Société des Jeux Mutuels Urbains. Prohibited on all racetracks, however, it is bet by intermediaries, which is prohibited. Dréant, he is a big scoundrel linked to the underworld and has compromising files on politicians in place. However Dréant has decided to "organize" the Prix de Belfort race. As he needs a lot of money for this, he calls - in his own way - on Loic le Guenn (Jacques Dutronc), a young and skillful politician. The latter will pretend to enter the scrapyard game but to better overwrite it and recover a compromising file. It will be enough for him to warn Chazerand who will play big and win a lot, then, the Racing Company refusing to pay, to deliver it to the scrap dealer and to draw his own pin from this game which no longer owes anything to chance.