In Turin in the winter of 1862, the unmarried Giorgio Bacchetti, a good-looking cavalry captain with a distinguished combat record, is involved in a passionate affair with Clara, a sweet and beautiful married woman.

This is a young woman named Fosca, suffering not only from a range of physical and psychological problems but also strikingly ugly.

Encouraged by the regimental surgeon, who thinks contact with the new arrival may help, Giorgio spends time with her.

While she thrives on what to her is a conquest, Giorgio is dragged down by the emotional strain of her demands on him and falls ill.

Fosca goes into massive hysterics, to the horror of the guests who had no idea of the existence and depth of her passion.