Hastings is present in the adaptation, while he was absent from it in the original novel.
Countess Vera Rossakoff's message to Poirot provides his impetus to travel to Baghdad, and from there is roped by Hastings into visiting the dig at Tell Yarimjah. In the original Poirot was pretty much just passing by.
Adaptation Dye-Job: Shiela Reilly is shown to be dark-haired in the book, while in the episode she's blonde.
A subplot regarding Poirot being summoned to Baghdad by Countess Rosakoff is added, with Poirot failing to meet her every time he looks for her.
Joseph Mercado's subplot is expanded upon in the episode.
Adapted Out: The characters of Dr. Giles Reilly, Carl Reiter and David Emmott are excised from the adaptation.
Artistic License – Geography: In the original book, Tell Yarimjah was situated near Hassanieh, implied to be in northern Iraq. In the episode, it's located a few hours away from Baghdad, allowing the characters to travel back and forth between the two locations, and for Poirot to have his creature comforts which he'd otherwise be deprived of at an archaeological site.
Ascended Extra: Amy Leatheran was the protagonist of the original novel, with Poirot only appearing midway through the story to investigate Louise Leidner's murder. Of course, Poirot is the focus of the TV series, so he's now the protagonist.
Continuity Nod: Countess Vera Rossakoff (last seen in "The Double Clue") provides Poirot with his impetus to travel to Baghdad in search of her, though she doesn't actually appear in person.
Demoted to Extra: With Poirot and Hastings present in the adaptation, Amy Leatheran's role is significantly reduced to that of a supporting character.
Drugs Are Bad: Joseph Mercado's drug addiction has such a hold on him that he ends up killing an Iraqi man named Izzat Baqui after their deal goes bad, and later decides to shoot himself due to the guilt.
Hypocrite: Hastings tries to lecture Poirot about women when the latter's attempts at contacting Countess Rossakoff are in vain, only for Poirot to point out that Hastings is undergoing a rough patch in his marriage (as his wife basically exiled him from South America).
Karma Houdini: Father Lavigny (or rather, his impersonator) and his confederate aren't mentioned to be arrested unlike in the original, and their last scene was the two of them escaping the dig site after they realize Poirot is on to them.
Promoted to Love Interest: With David Emmott removed from the adaptation, Bill Coleman is now paired with Shiela Maitland instead, though it's left ambiguous what happens after they start dating.
Bill Coleman is made Hastings' nephew by adoption. This leads to Hastings reacting in disbelief when Poirot theorizes that Bill Coleman may be Frederick Bosner's brother William.
Shiela Reilly is made Superintendent Maitland's daughter instead, since Giles Reilly, her father in the original story, was Adapted Out.
"Shaggy Dog" Story: Poirot is summoned to Iraq by Countess Vera Rossakoff, and he goes to Baghdad to meet up with her, which he keeps on failing every time. At the end of the episode, it's revealed that the Countess has been in Budapest for a while, and Poirot is understandably annoyed at this revelation.
Alternative Title(s):Poirot S 08 E 03 Murder In Mesopotamia
