"Désirée’s Baby" has a serious and detached tone. Because the story uses a third-person perspective, there is little judgment or interference from the narrative voice. Instead, the story’s tone is shaped by the observations of the characters and by Chopin’s use of descriptive language.
The first section of the short story relies heavily on Madame Valmondé’s memories. As she reminisces, the story takes on her sense of anticipation. Madame Valmondé loves Désirée and thinks of her fondly, but she feels concerned for her adopted daughter. Once she arrives at L’Abri, there is a transition and the tone becomes more ominous. Chopin builds tension passively, using description without much in the way of explicit commentary:
Madame Valmondé had never removed her eyes from the child. She lifted it and walked with it over to the window that was lightest. She scanned the baby narrowly, then looked as searchingly at Zandrine, whose face was turned to gaze across the fields.
It's evident in this moment that Madame Valmondé suspects that Désirée's baby isn't white—but the narrative never explicitly says this. Instead, the narrator maintains a reserved, almost withholding tone, simply focusing on simple descriptions of Valmondé's actions rather than going on at length about her suspicions. In turn, this sparse tone encourages readers to actively search for details that might clarify what, exactly, is going through the characters' minds.