The novel delves deep into how uncontrollable passion can override moral judgment, leading seemingly ordinary people to commit extraordinary acts of evil. The relationship between Frank and Cora exemplifies how sexual desire can become a catalyst for violence and destruction.

Through its intricate plot, the story demonstrates that wrongdoing never goes unpunished, even if not through conventional means. The title itself is a metaphor for how justice, like a persistent postman, always delivers its due, sometimes requiring multiple attempts.

The narrative presents a dark critique of the American Dream, showing how the pursuit of happiness and freedom can become corrupted by greed and lust, leading to moral degradation and ultimately, self-destruction.