In a rough neighborhood of Paris in 1914, atheistic sewer worker Chico (James Stewart) rescues a young woman named Diane (Simone Simon) being beaten by her sister Nana (Gale Sondergaard) for not being nice to an older man, a patron in the sister's disreputable dance hall. Father Chevillon (Jean Hersholt) is determined to convert Chico. Chevillon learns from Boul, Chico's taxi driver friend, that Chico gave God a chance, but nothing came of it. The priest grants Chico's first prayer, getting him a promotion to street washer. He then gives Chico two religious medals for protection. Chico is amazed to discover that they are made of real silver; a price tag reveals they are worth twelve francs - exactly the cost of two candles he purchased in church for his prayers.