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.

Auguste, a somewhat simple-minded Provençal fisherman, loves and admires Mireille. This concerns only Maurice, son of an important wholesaler, whom scruples do not stifle. Seduced and abandoned, Mireille moves Auguste who tries to mend his poor happiness. The local priest, with wise words, leads Mireille to offer her hand to Auguste.

Pierre can no longer pay for his medical studies and disappears for several months. During his absence, his fiancée allows herself to be courted by a reveler. Back home, Pierre cannot regain the trust of the young woman, who now leads a dissolute life of which she is ashamed. She tries to kill herself. Pierre saves her and heals her.

Sylvio, a successful singer, has found a way to take a peaceful vacation, safe from his female adulators: to travel incognito. He puts up at an old castle whose landlord, Count Fabrice, a ruined nobleman, seeks a hidden treasure. Posing as the nephew of the castle gardener, Sylvio enjoys happy days and even finds the time to fall in love with Gracieuse, the count's daughter. Unfortunately for him, his impresario ends up locating him...