Saki's short story "Dusk" explores themes such as deception, human nature, and the dangers of judging by appearances. The protagonist, Norman Gortsby, believes he can read people well but is ultimately deceived by a con artist. The story highlights the inscrutability of human motives and the capriciousness of fate, as Gortsby's assumptions lead to his downfall. Set at dusk in a London park, the story uses the fading light as a metaphor for uncertainty and the blurred lines of truth.