In the Po Valley during the 19th century, a rich girl engaged to a well-to-do farmer ends up penniless and is forced to work for her fiancé’s relatives. Peasant unrest, carried to extremes by both workers and landowners, leads to violence and tragedy.

Unlike most Italian films of the 1940s, Augusto Genina's Cielo Sulla Palude opened in Venice rather than Rome. The film's American title was Heaven Over the Marshes, and indeed most of the story is set in the disease-ridden Pontine Marshes on the outskirts of Rome. This was the home of Maria Goretti, a pious young girl who was murdered by her would-be seducer. For reasons elucidated in the course of the film, Maria's short time on earth made her worthy of Sainthood, which was actually bestowed upon her shortly after the release of this film. Maria Goretti is well-played by Ines Orsini. Cielo Sulla Palude served as the comeback feature for director Augusto Genina, whose previous pro-fascist films had caused him to be blacklisted after WW II.

Franco, a young man of noble descent, marries Luisa, daughter of a humble clerk, against his grandmother's will.