The arrival of a manipulative outsider threatens to dismantle the carefully constructed domestic stability of a long-married couple. Hilda and Rupert Foster find their twentieth anniversary preparations disrupted by the machinations of Julius King, a cynical intellectual who orchestrates a complex social experiment to test the integrity of their relationships. The narrative operates through a third-person perspective that shifts between the members of a tight-knit social circle, exposing the fragility of human virtue when subjected to calculated psychological pressure. The world is defined by the intellectual and social constraints of the British upper-middle class, where moral posturing often masks deeper insecurities.

Readers and critics frequently note the sharp, cynical wit that permeates the narrative, often comparing the work to a modern morality play. Discussion often centers on the effectiveness of Julius King as a catalyst for revealing the hidden flaws within the other characters. Many observers highlight the balance between the novel's realistic domestic setting and its underlying allegorical weight. The pacing is described as deliberate, allowing for deep psychological exploration rather than rapid plot progression. Readers often find the exploration of how individuals justify their own moral failings to be the most compelling aspect of the text.