In the very first chapter, Agatha Christie makes an allusion to perhaps the greatest-known fictional detective of all time—Sherlock Holmes:
“Well, I’ve always had a secret hankering to be a detective!”
“The real thing—Scotland Yard? Or Sherlock Holmes?”
“Oh, Sherlock Holmes by all means.
Sir Arthur Conan Doyle’s Sherlock Holmes stories are quintessential to understanding the development of detective fiction. In the passage above, it is notable that Hastings tells Mary Cavendish that he wants to be like Sherlock. Although Hastings idolizes his fictional predecessor and wishes to be a detective of a similar caliber, throughout the novel he proves himself to fit much more closely as a match for the famed detective's more ordinary counterpart—Watson. Both Watson and Hastings serve as reader stand-ins in their respective series, allowing the readers to have a character within the novel who discovers information at their own speed rather than the lightning-pace of the more accomplished mystery-solving detectives. This inflated, dreamed-up desire of Hastings demonstrates his vibrant personality, priming the reader to be on the watch for his emotional, exaggerated idealism. Furthermore, Hastings’s early invocation of the Sherlock stories is one of the first hints that a mystery will soon arrive to overwhelm Styles Court.
Evelyn Howard’s argument with John Cavendish midway through Chapter 5 regarding her belief in Alfred Inglethorp’s guilt is steeped in layers of situational irony, particularly considering Hastings’s own musings as he recounts these events from memory:
It occurred to me very forcibly at that moment that to harbour Miss Howard and Alfred Inglethorp under the same roof, and keep the peace between them, was likely to prove a Herculean task, and I did not envy John. I could see by the expression of his face that he fully appreciated the difficulty of the position.
In the passage above, Hastings recognizes Evelyn’s distaste for Alfred in light of her verbal insistence on the man’s guilt. It is this perceived animosity that leads Hastings to assume that John Cavendish will have a hard time balancing Evelyn and Alfred together. However, Hastings's observation that Evelyn and Alfred are enemies who find it difficult to civilly converse is deeply ironic in light of the later revelation of their amorous, murderous affair. The allusion he makes here to Hercules—the Greco-Roman mythological figure whose fame is owed to his divine, god-given strength—reflects how deeply he believes the pair dislike each other and how well their ruse is working on him.