The mood of "A Pair of Silk Stockings" is introspective and melancholy. Despite Mrs. Sommers's initial optimism about her plans to spend the fifteen dollars on her family and her brief excitement about the alternative purchases, the story turns out to be gloomy. Each material object is described in such a removed way, and Mrs. Sommers's excitement is portrayed in such a grandiose way, that the reader might (rightfully) struggle to believe that there is any true joy in her actions.
The joy indeed turns out to be false—or at least very short-lived. The final passage makes the gloomy mood inescapable:
A man with keen eyes, who sat opposite to her, seemed to like the study of her small, pale face. It puzzled him to decipher what he saw there. In truth, he saw nothing—unless he were wizard enough to detect a poignant wish, a powerful longing that the cable car would never stop anywhere, but go on and on with her forever.
This final passage encourages readers to reconsider the playfulness of the story, which began in a rather lighthearted way. It's now clear that Mrs. Sommers found only short-term happiness during her day in the city and will now return to her motherly responsibilities. Her "powerful longing" for freedom eclipses every other moment of longing for the stockings, for a nice meal, or to see a show at the theater, ultimately leaving Mrs. Sommers—and, in turn, readers—in a poignant state of dejection and disappointment.