Madame Clapain dies in dubious circumstances at the home of the Cadifon ladies, of which she was a tenant. A friendly inspector and Thérèse Cadifon each carry out their own investigation.

The story of how the people of Paris cope with the strains and struggles of war, from the siege of the city by the Prussians during the Franco-Prussian War of 1871 to the invasion by the Germans in World War II.

Following a broadcast on the radio, each of the listeners remembers these "little nothings" (the title is borrowed from a play by Mozart), which have often changed their lives. Each of these stories told will prove that a tiny detail in life can change an entire destiny.

Félix Raffut, a Périgord squire terrified by the German invasion, carries out the exodus of his family and his furniture towards supposedly hospitable places.

Jean Vernet, an unselfish banker, feels fine : he has a charming mistress, Jacqueline ; a godson, Fernand, that he took in when he was a child and that he has brought up and cherished ever since ; a faithful friend, Lamblin ; and an adorable dog. But things are not so rosy as they look. Adrienne, Jean's sister, hates Jacqueline and is prepared to do everything to separate the couple. Worse, it looks as though Fernand has betrayed his godfather by sleeping with Jacqueline. To know more about those around him, Jean, a modern Volpone, decides to fake deafness.