In the film "A fuego lento," Guadalupe Palma, a dancer and part-time prostitute, finds herself at the center of a suspenseful and enigmatic story, inadvertently setting off a chaotic pursuit by various factions, including ruthless gangsters. Her impoverished musician boyfriend, Óscar, becomes entangled in the intrigue, resulting in a unique cinematic experience with minimal dialogue.

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.

Ernesto, a composer, is madly in love with Amalia. He decides to help her pay the rent and wants her to start singing at the cabaret where he works, but she ends up falling in love with another man.