Although the entirety of the novel occurs after her death at the hands of Mr. Ratchett, also known as Cassetti, Daisy Armstrong plays a major role in the trajectory of the narrative. A three-year-old girl from a prominent American family, her kidnapping and murder spurred national outrage and destroyed the fabric of the Armstrong family’s lives. The significant impact that her loss had on those around her serves as the foundation of Murder on the Orient Express as the twelve passengers on the train vow to deliver the justice that Ratchett escaped in America. While Christie crafts the details of the Armstrong case in a way that allows her to explore the ethics of vigilante justice, the basic structure of the crime derives from the real-life kidnapping of Charles Lindbergh Jr. in 1932. The infant son of famed pilot Charles Lindbergh was stolen from the family’s New Jersey home with a ransom of $50,000 demanded for his return. As was the case with Daisy, Lindbergh Jr.’s body was found after the family paid the ransom, and the story made national headlines. By drawing inspiration from a real-life story familiar to her 1934 readers, Christie takes advantage of the public’s sympathy to enhance their emotional investment in her fictional characters.

Beyond the similarities between the Lindbergh case and the Armstrong case, Christie includes very specific details throughout the novel to emphasize Daisy’s status as a figure of goodness and innocence. The choice of the name “Daisy” itself carries symbolic value as the simple, white flower often represents purity. She has a natural, unburdened spirit which sets her apart from the corrupt world that Ratchett represents, and this quality evokes adoration from everyone present in the Armstrong household. Almost every train passenger who talks about Daisy does so in a detailed way, emphasizing just how special her presence was in their lives. Countess Andrenyi, who is really Daisy’s aunt Helena Goldberg, cites her perfect, angelic curls while Antoinio Foscarelli, the family chauffer, tears up as he tells a story about Daisy pretending to drive the car. 

Including these specific details about Daisy allows her to become a more fully realized character even though she never appears in the novel herself. Rather than taking a generalizing approach to her identity as an innocent victim of crime, Christie emphasizes Daisy’s humanity and individuality in order to heighten readers’ investment in the tragedy. Knowing that this symbol of goodness has been destroyed creates an emotional void, and although Ratchett’s death does not restore the purity that Daisy represented, it fills the emptiness that his crime causes. Without the heart-wrenching pull of Daisy’s character, this dynamic, and therefore Christie’s commentary on moral justice, would not have been possible.