The novel explores the intricate dynamics between Agatha, her husband Archie, and his mistress Nan. While societal expectations might paint Nan as a simple homewrecker, de Gramont fleshes out her backstory, revealing a woman driven by her own personal tragedies and desires. The reader is challenged to confront their own biases and understand the nuanced motivations driving each character in this complex love triangle.

Both Nan and Agatha are haunted by their pasts. Nan carries the scars of a forbidden love and a devastating loss from her childhood in Ireland, while Agatha grapples with the recent death of her mother and the crumbling facade of her marriage. De Gramont skillfully interweaves these past experiences into the present narrative, demonstrating how past traumas can shape present actions and fuel unexpected reactions.

Secrets act as a driving force throughout the novel. Nan's hidden past and her connection to Agatha's disappearance form the central mystery. Agatha, too, harbors secrets, both personal and professional, that add layers of intrigue to the story. "The Christie Affair" reminds us that everyone carries secrets, and sometimes, those secrets can have life-altering consequences.