Alex Grégoire is a timid insurance company clerk who shares his uneventful life between his wife Angèle, his colleagues and his passion for crosswords. But all of a sudden his existence changes dramatically. First because he wins a crossword competition. Second because a jewel thief, Charles Tuffal, thinks he recognizes in him a former accomplice. From that moment "uneventful" is not the best adjective to qualify Alex's life anymore...

A rich young man, Pierre Trévoux, has a desire for adventure and boasts of his courage. While he is staying with friends in the countryside, his hosts, to play a trick on him, organize a fake burglary, but he discovers the hoax. When he returns home, he finds his house broken into. Convinced that the game continues, he does not understand that he is dealing with real gangsters. His recklessness allows him to rout the criminals.