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.
- Antagonistin Mourning: Dr Leidner truly loved his wife, even though he had to murder her for straying. While he makes attempts to detract from the investigation, in the end once he is found out he quietly admits his crime.
- Arc Words: Murder is a habit.
- 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.
- 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 in Murder In Mesopotamia 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.
- It's Personal: Poirot suspects the murderer could be a relative of Frederick Bosner, Mrs. Leidner's late first husband.
- Jerkass Hasa 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.
- Moral Event Horizon: Dr Leidner crosses it when he murders Miss Johnson, as he himself admits.
- Personal Effects Reveal: How Miss Johnson discovers who the murderer is.
- She Knows Too Much: Miss Johnson.
- 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 is the narrator of the story and Poirot's assistant in this case.
- 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.