To accurately identify the primary theme of the excerpt from H. H. Munro's story "Dusk," I would need to see the specific passage you are referencing. However, I can provide a general understanding of the themes commonly present in Munro's work, particularly in "Dusk."
Themes often explore the contrast between appearances and reality, the darker sides of human nature, and social satire. "Dusk" frequently highlights the nuances of human behavior, the significance of social context, and the complexities of moral judgments.
If you provide the excerpt, I can offer a more precise analysis of its theme.