Chico, a sewer worker in Paris, meets Diane, a girl oppressed by her cruel sister, Nana. When Nana kicks Diane out onto the street, Chico takes her in to his run-down 7th floor flat. Although Diane starts falling in love with him, the cynical Chico feels nothing in return until Father Chevillon, a local priest, helps him to find a better job as a street cleaner. Chico's self-respect improves and he considers marrying the girl. When Chico is sent to fight in World War I, he and Diane vow to think of one another every night at eleven o'clock.