During a visit to an archaelogy dig in the Middle East, Poirot is faced with investigating the murder of Louise Leidner, the wife of famous archaelogist Dr. Eric Leidner.
Many years ago, she had been married to Mr. Bosner, a covert spy, who died tragically in a train accident. After his death, she began receiving death threats (allegedly by her former husband) warning her not to remarry. However the letters had abruptly stopped when she married Dr. Leidner. But, sometime before her death, she had received another letter and had begun seeing visions of a face in her bedroom window at night. Poirot soon suspects that someone at the dig knows of Mrs. Leidner's past marriage and is possibly related to her late husband...
Other characters include fellow archaelogists Richard Carey, who hated Mrs. Leidner, Miss Anne Johnson, devoted friend of Dr. Leidner, David Hemmot, a young professional, and Joseph Mercado, a nervous and timid man. Besides these, there's Mrs. Mercado, who also disliked Louise Leidner, nurse Amy Leatheran, who came to treat the victim of her increasing nerves, Bill Coleman, an expert on ancient objects, Carl Reiter, the dig's photographer, Father Lavigny, an expert of old languages, and Dr. Reilly and his daughter Sheilla, two local residents.
The novel was adapted into an episode of series eight in the ITV series Poirot. Tropes unique to this adaptation are listed on the page for the series.
This novel provides examples of:
- Adventurer Archaeologist: Most of the main characters.
- A Father to His Men: Dr Leidner, despite his modest attitude, has great authority and command over his group. This reflects in his planning the murder, when everyone got tense and edgy.
- Affably Evil: Dr. Leidner is quite charming, is liked and respected by the members of his party, and is honestly sorry for killing Miss Johnson. However, he was also a convicted spy, and is possibly the biggest male Yandere in Christie fiction, stalking his wife for YEARS, keeping other men away from her until he has a chance to re-woo her instead.
- Antagonist in Mourning: Dr Leidner truly loved his wife, even though he had to murder her for what he saw as straying (he was a German spy in the first World War). While he makes attempts to detract from the investigation, in the end once found out he quietly admits his crime.
- Arc Words: Murder is a habit.
- Asshole Victim: According to Sheila, Louise really, really had it coming after screwing with so many people for her own amusement.
- Attention Whore: Louise Leidner was this, according to many people.
- Call-Forward: According to the epilogue, Poirot travels home on the Orient Express. Also a Call-Back since Murder in Mesopotamia was published two years later.
- Cassandra Truth: Louise Leidner is in fear of her life from her first husband, but nobody really took it seriously until her murder happened. In fact Poirot at first assumes her murderer is one of the members of the expedition, though he is able to get on the right track at the end.
- Dead Person Impersonation: Dr. Leidner is really Frederick Bosner.
- Death by Looking Up: Miss Johnson correctly deduces that this was how the murder occurred. Unfortunately the murderer was present when she learns this so she ends up being killed.
- Extreme Doormat: Carl Reiter. Poirot actually takes a break from his case speech to tell him to handle himself better.
- Gaslighting: Dr Leidner did a bit of this to make people assume his wife made up the threats on her life.
- Hoist by His Own Petard: If Dr. Leidner hadn't killed Mrs. Johnson, Poirot would never have tracked him down.
- Hypocritical Heartwarming: Dr. Leidner defends his people as being incapable of murder. Of course they didn't kill his wife, because he's the one who did it.
- If I Can't Have You...: The constant threat for Louise is that her supposedly dead husband will kill her for being with another man. It turns out that her husband survived the train crash that supposedly killed him. When he took on the identity of Dr. Leidner, he married Louise (again) and stopped sending the threatening letters. However, when she started an affair with an another man, he decided to carry out his threat, preferring her dead than with someone else.
- Ignored Enamored Underling: Miss Johnson clearly pines for Dr. Leidner. He only has eyes for his wife, and doesn't stop him from killing her by replacing the water on her nightstand with hydrochloric acid.
- I'll Take That as a Compliment: When Poirot describes how David Emmot has the methodical temperament that would be suitable for a murderer, Emmot wryly (yet sincerely) says "Thank you."
- Impersonation-Exclusive Character: We really never learn anything about Eric Leidner, besides that he was a Swedish archeologist. That's because it's revealed he died decades ago in a train crash, and his identity was stolen by German spy Frederick Bosner. Likewise, we never find out what sort of person Father Lavigny is. All the time in the book, he has been impersonated by a jewel thief, as the real Father Lavigny fell sick and was unable to accompany the expedition at all.
- It's Personal: Poirot suspects the murderer could be a relative of Frederick Bosner, Mrs. Leidner's late first husband.
- Jerkass Has a Point: Sheila Reilly is ready to speak ill of the recently deceased, but only because theyre dead and beyond any damage that slander could do to them, while speaking ill of the living can do more harm and requires more tact.
- Locked Room Mystery: Louise Leidner had locked her bedroom door, its only entrance, before her death, and it was also impossible to get in through the window since it was barred.
- Love Makes You Evil: Dr. Leidner.
- Personal Effects Reveal: How Miss Johnson discovers who the murderer is.
- He Knows Too Much: Miss Johnson figures out how the murder was committed... unfortunately, the murderer also figures out that she figured it out.
- This Cannot Be!: Dr Leidner cannot believe that anyone in his expedition could have a reason for killing his wife.
- Troll: Dr Reilly can't resist taking a dig at Nurse Leatheran when she is counted as a suspect. It's in good humor though and he doesn't take it too far.
- Unreliable Narrator: Nurse Leatheran narrates the story, and admits that despite her she is biased strongly towards people she likes (Mrs Leidner) and against people she dislikes (Sheila Reilly). Subverted though; despite her opinions, she is able to tell her story competently and objectively enough.
- The Watson: Nurse Amy Leatheran is the narrator of the story and Poirot's assistant in this case.
- What Happened to the Mouse?:Frederick Bosner's brother is a possible suspect but nothing comes of this due to Frederick himself being the culprit, and it's never revealed if he informed his brother of his survival.
- Yandere: Dr. Leidner a.k.a. Frederick Bosner is an extreme example, resorting to threatening letters, a Dead Person Impersonation, and even murder to stop his wife from straying.