Original Airdate: 11 August 2014 Written by: Nick Dear Directed by: John Strickland Recurring cast: Ariadne Oliver Based on:Elephants Can Remember
Tropes:
Adaptation Expansion: A drastic example: the adaptation adds an entire additional murder victim, investigation, and killer taking place 13 years after the one in the novel.
Downplayed. While Willoughby the Elder certainly treated Dorothea Ravenscroft for her mental issues, there's no mention in the novel that she was subjected to "hydrotherapy". While Willoughby used it to treat Dorothea, he later regrets using the method and never uses it again.
His son isn't much better off in the adaptation either. The younger Willoughby is shown to have a wandering eye, a fact that Mary Jarrow exploits to allow her access to his father and to provide an alibi for herself, and exploits said affair to erode Willoughby's relationship with his wife and to erode his own alibi as well.
Aliens Speaking English: Poirot visits Zélie Rouselle in her shop in Paris, and yet the two have their conversation in English rather than in their mutual native language, French.
Almost Dead Guy: After being pushed off of a cliff, Margaret Ravenscroft lasts long enough to give Desmond and Zélie her last instructions to prevent Dorothea from being committed to therapy again.
And This Is for...: It is revealed after Margaret Ravenscroft was killed, General Alistair Ravenscroft has to take her murderer/sister Dorothea to the same cliff that she pushed Margaret off. Once they were there, General Ravenscroft exposed the villainy and said, "This is for Margaret," before fatally shooting Dorothea, and then concluded, "And this is for me," before shooting himself.
Ascended Extra: Marie McDermott a.k.a. Mary Jarrow, daughter of Dorothea Jarrow, was only briefly mentioned (and not by name) in the original novel.
Best Served Cold: Mary Jarrow waited over a decade to get vengeance on the man who tortured her mother in the name of psychiatric treatment.
Big Damn Heroes: Detective Inspector Beale arrives just in time to save Celia from falling off a balcony.
Burial at Sea: We discover that after Dorothea Jarrow killed her twin sister Margaret Ravenscroft by pushing her off the cliff, her husband General Alistair had to keep his promise by giving her a decent burial at sea along with Zélie Rouselle.
Composite Character: Zélie Rouselle corresponds to the original novel's Madame Rouselle and Zélie Meauhourat.
Death by Adaptation: Dr Willoughby the Elder's death becomes the inciting incident in the adaptation; in the book he remains alive throughout.
Evil-Detecting Dog: Lady Ravenscroft's dog knows something is wrong with its mistress.
Green-Eyed Monster: This is revealed to be Mary Jarrow's motive for attempting to kill her own cousin Celia Ravenscroft. While her motive for killing the elder Willoughby was revenge for her mother's maltreatment, her motive for killing her cousin boils down envy at Celia leading a happy life while Mary hadn't.
In the Blood: Both Dorothea Jarrow and her daughter Mary are shown to be mad enough to be willing to kill their own family for their own ends.
It's for a Book: Used as a cover by the killer; mildly lampshaded in that even the killer is surprised that the victim fell for it.
Karmic Death: Dr Willoughby is murdered by being drowned in the same tub that he used to subject patients to "hydrotherapy".
Match Cut: The shot of Dorothea Jarrow falling off of a cliff in a flashback is matched to Ariadne Oliver dropping a sugar cube into her cup of coffee.
Ooh, Me Accent's Slipping: In-universe. Marie passes herself off as from Boston, but Poirot catches some pronunciation slips that indicate that she's actually Canadian.
Spotting the Thread: Poirot realizes Marie isn't from Boston because she says "zed" rather than "zee" and because she's unaware of where she was on St. Patrick's Day; an Irish-American wouldn't be caught dead forgetting about said holiday.
Two Lines, No Waiting: Ariadne Oliver's and Poirot's respective investigations leading up to a Halfway Plot Switch when it becomes clear that the murders are linked.
Woobie, Destroyer of Worlds: Canon Foreigner Mary Jarrow, daughter of Dorothea, the murderess from the original book. Embittered and traumatised by her mother's death and blaming her mental instability on her treatment at the Willoughby Institute, she spent her life saving up to move back to England so that she could take murderous revenge.
Working the Same Case: Poirot investigates Prof. Willoughby's death while Oliver investigates the Ravenscrofts, but the two murders turn out to be closely linked.
