In "Miss Brill," Mansfield creates a mood of determined cheerfulness that gradually fades into despair. Miss Brill's loneliness is immediately apparent from her solitary venture to the park, where most visitors seem to be accompanied by family or friends. Miss Brill valiantly presents herself as a contented participant in a communal scene, rather than a lonely outsider. But the reader can discern this isn't really the case. Immediately after watching a group of girls pass arm in arm, their friendship emphasizing her solitude, Miss Brill expresses emphatic delight with her outing, even comparing herself to an actress in a play:
Oh, how fascinating it was! How she enjoyed it! How she loved sitting here, watching it all! It was like a play. It was exactly like a play.
The contrast between Miss Brill's statements of happiness and the details revealing her loneliness show that the story's cheerfulness is just a facade.
When the young couple audibly mocks Miss Brill, calling her a "fried whiting," she's forced to acknowledge that other people view her as pitiable and repulsive, just as she dismissed the old people in the stands earlier in the story. At this point, Miss Brill abandons her pretensions of happiness and belonging, and the mood becomes darker. In its final passages, the story obliquely expresses Miss Brill's despair by showing how she foregoes her usual stop at the bakery. It ends with a blunt description of Miss Brill's "dark" and "cupboard"-like room. Since Miss Brill never explicitly expresses her own loneliness, the reader feels it even more intensely.