Sherlock Coco, famous detective, tries to thwart the machiavellian plans of the trio of shock. Croquignol, Ribouldingue and Filochard must be extra vigilant, but the profit motive is too strong. As a corollary, the famous pink diamond is also of interest to their legendary enemy, Jo Papillon. But always inventive, they will work out multiple scams and tricks to reach their goals.

Although suspected and hunted down by policeman Sherlock Coco and inspector Hector, the Pieds Nickelés (Croquignol, Filochard and Ribouldingue) manage to save the legacy of Monsieur Miradoux, who will be very grateful to them.

After a crazy night spent at Maxim's, Doctor Montgicourt returns home with the Môme Shrimp. General Petypon invites her to his castle for the engagement of his niece and Lieutenant Corrignon, the kid's lover. The reception is likely to be very busy...

The Bontemps family, like all the inhabitants of the village of Coussy la Chapelle, are passionate about radio. Coco, the fiancé of Jacqueline Bontemps, participates in all the contests and under the name of Mr. Bontemps wins a beautiful Sunday. All arrive in Paris and in the premises of the Parisian Post Office attend popular broadcasts.

In order to inherit her husband's old aunt more quickly, a greedy peasant woman engages in various dishonest maneuvers.