Mary Debenham is next, and Poirot finds her uncooperative, giving noncommittal responses to each question and claiming ignorance. Unlike some other passengers, she merely shrugs when she hears the nature of Ratchett’s murder and notes that “people die every day.” Poirot responds that “you are very Anglo-Saxon.”
Poirot’s is frustrated with Mary Debenham for many of the same reasons as he was with Arbuthnot. They both display an “Anglo-Saxon” sensibility that mostly manifests as a refusal to show any emotion or curiosity whatsoever. In response, Poirot attempts to get a rise out of Mary through reference to her nationality.
Poirot says what Mary is thinking: that she’s contemptuous of the way he conducts the investigation and that she would prefer an “English inquiry,” “cut and dried” with everything in its proper place. He says this with a “twinkle” in his eye. Poirot states that he reserves the right to his “little originalities” and notes that he tailors his method to the witness. He claims that, for her, he asks probing questions about her thoughts and feelings.
Poirot’s monologue here is notable as a justification for his entire method of inquiry and indeed Christie’s larger approach to the detective novel. There may even be an allusion to Sherlock Holmes in his reference to “English inquiry.” In any case, Poirot’s investigation is disorganized in much the way people are, and his focus on psychology rather than physical evidence means that few things can be “cut and dried.” Further, Poirot has shown that the “twinkle” in his eye is a sign that he’s hit on a productive avenue of inquiry, and the way he presses Mary Debenham suggests that she may be hiding something.
Ms. Debenham recites her recent history as a governess in Baghdad. Poirot mentions that he assumed she would be married soon, which Ms. Debenham calls “impertinent.” He also asks her whether she owns a scarlet kimono and she responds, “No that is not mine.” Poirot follows it “like a cat pouncing on a mouse” and Ms. Debenham reveals she did see someone in a scarlet kimono when she woke this morning at five but didn’t recognize the person.
Just as Poirot antagonized Arbuthnot by suggesting that he felt “warmly” towards Mary Debenham, he provokes Mary by suggesting that she might be married soon, a reference to her relationship with Arbuthnot. This approach, as well as Poirot’s close attention to the language of the suspects in his interviews, bears fruit when Mary reveals a hidden detail: she also saw the woman in the scarlet kimono. Notably, she saw the woman at five in the morning when Poirot had seen her closer to two.
Before she leaves, Ms. Debenham says that her roommate, the Swedish woman Greta Ohlsson, is worried that she’s a suspect for the murder as she was the last to see Ratchett alive. Poirot confirms Greta’s alibi and tells Ms. Debenham that Greta is not a prime suspect.
Even faced with an unlikely suspect, a gentle older Swedish woman, Poirot is reluctant to rule her out as a suspect until her alibi is confirmed. Even then, reassuring Greta may be a strategy on Poirot’s part, and there’s a sense that he still views every passenger as a potential suspect.