The title of the story refers to malarial fever, which was prevalent in Rome before the draining of the swamps around the early nineteenth century. This fever was much feared by American tourists, especially those who had young, fragile daughters who might succumb to the ravages of the disease. The chances of contracting the disease were increased greatly after dark, when the mosquitoes that spread the infection were most active. Symbolically, the title also refers to the fever pitch of the passions that were engendered in the two women when they visited Rome as nubile young girls. The surface serenity and static nature of the plot provide ironic contrast to the gradual revelation of the intense emotions that the two women experienced when they were in Rome before.
The story contrasts the abiding hate of Alida Slade with the abiding love of Grace Ansley. Alida’s cruelty and hatred, aroused by her fear that Delphin might be attracted to Grace, prompts her finally to reveal her trickery to the other woman. Her intention was clearly to humiliate the other and to bask in her triumphant superiority. Grace reveals, at Alida’s goading, that the trickery not only did not work but also was actually the impetus for the birth of Barbara, the child for whom Alida has envied Grace ever since the child was an infant.
Friendship and companionship are superficial social amenities as depicted in this story. Strong emotions are suppressed or at least concealed in favor of outward tranquillity and smooth social relations. However, the deep, hidden emotions have nevertheless driven these women to actions that shaped their lives and characters in profound ways.