A young customs officer is given an important mission: to investigate drug trafficking on the Belgian border. Incognito, he goes to the place where he easily spots the gangsters.
A prompter at the Folies-Bergères and admirer of a lovely dancer, the man named Jules has the unpleasant surprise of finding, one fine morning, the corpse of his beloved in a trunk. An investigation, more burlesque than tragic, will give a lot of trouble to Jules who will have great difficulty in proving his innocence.
Émile Boulard is a props man in a Paris movie studio. He has a wife, Suzanne. Or to be more accurate, let's say he HAD a wife since she left him fifteen years before, allegedly ... to go buy a post stamp. But now that their daughter Martine , who lives with her, is old enough to marry, she resurfaces. She confesses that, in order to explain his absence, she has told Martine her father was a great explorer and lion hunter in Africa. Not to disappoint his daughter, Émile accepts to pose as the adventurer he is supposed to be. At the same time he will help Daniel, Martine's bashful fiancé, not to become a henpecked husband like him.
In the village of Sableuse, the local manor has been bought out by a nouveau riche, Emile Cousinet. When his wife Lisette, a former music hall actress, flees to Paris with young Pierre de Sableuse, Cousinet asks Father Pellegrin, the village vicar, to bring the lost sheep back home.
Alphonse and his wife Zulma hold the 421, a tavern in the outskirts of Lille, in the North of France. It is always full of regulars who play cards there and drink gin and exchange words in ch'timi, the local patois. But there has been trouble lately: felonies have been committed in the surroundings. So who can be those two strangers who have just rented a room each at the 421? Each sets about doing a bit of detective work.