Chapter IV of “The Mysterious Affair at Styles” by Agatha Christie delves deeper into the investigation, with Hercule Poirot beginning his own probing into the murder. The chapter opens with the narrator describing a path through the grass leading to the Belgians’ residence, where Poirot lives. Upon his arrival, the narrator quickly informs Poirot about the tragedy, seeking his help in investigating Mrs. Inglethorp’s murder.

Poirot, intrigued, listens intently to the details of the incident, emphasizing the importance of seemingly trivial facts and dismissing nothing as irrelevant. He particularly focuses on Mrs. Inglethorp’s last night’s dinner and her behavior, hinting at strychnine poisoning due to the delayed effects observed, a detail that confounds the straightforward nature of the case.

Following this, Poirot, accompanied by the narrator, visits the crime scene to collect evidence firsthand. He meticulously examines the room, noting several curious items: a shattered cup, a purple dispatch case with a key, a lamp with a broken chimney, and candle grease on the floor. An unexpected discovery of a half-burned fragment of a will among the ashes in the fireplace further complicates the investigation, suggesting a possible motive for murder revolving around an inheritance.

Poirot’s thorough investigation then leads him to interview Dorcas, a servant, and Annie, a housemaid. Their testimonies shed light on Mrs. Inglethorp’s distressing last evening, her quarrels, and peculiar behaviors, such as the special interest in a lost key and an unmarked box of sleeping powder found in her room. The housemaids’ accounts of the last night’s events, particularly about a cocoa drink and a missing green dress, serve to deepen the mystery rather than provide clarity.

Towards the end of the chapter, Poirot’s dialogue with the housemaid Annie hints at the possibility that the cocoa, not the coffee as initially suspected, was poisoned. This revelation shifts the focus of the investigation and opens up new avenues for inquiry. Despite the narrator’s excitement over this development, Poirot remains calmly analytical, subtly hinting that the solution to the murder lies in understanding the seemingly insignificant details they have unearthed, though he keeps his suspicions close to his chest.

The chapter exemplifies Poirot’s methodical and meticulous approach to detective work, emphasizing logic, the importance of minute details, and the need to withhold judgment until all evidence is carefully considered. His playful teasing of Hastings, who represents the reader’s impulse for quick solutions, serves to underline the complexity of the case and the need for patience in unraveling it.