The murders of Lesley Ferrier and Leopold Reynolds are elucidated in the adaptation; Garfield stabbed Ferrier and drowned Leopold.
The adaptation confirms that Michael and Rowena were behind Mr Drake's death, with Michael hitting him with his car. Poirot also hints at possible foul play in the death of Mrs Llewellyn-Smythe, though he chooses to ultimately leave that up to the police for investigation.
Adaptational Badass: It's Poirot himself who comes to Miranda's rescue, whacking Michael Garfield with his cane. In the original it was two boys named Nicholas Ransom and Desmond Holland who rescue Miranda at Poirot's behest.
Adaptational Early Appearance: Poirot first meets Michael Garfield on the train heading to Woodleigh Common rather than at his garden as in the original.
Adaptational Job Change: Elizabeth Whittaker was a maths teacher in the novel, but is a church organist in the adaptation.
Adaptational Sexuality: Beatrice White and Elizabeth Whittaker are revealed to have been lovers in this version. In the novel, two teenage boys actually gossip about this possibility, but it's never treated seriously.
Adapted Out: Several characters are excised from the adaptation, including Charlotte Benfield, Ann Reynolds, and recurring character Superintendent Spence.
Age Lift: Leopold Reynolds from goes from being Joyce's nine-year-old younger brother to her teenage older brother.
As the Good Book Says...: We hear Reverend Cottrell recite the KJV version of Luke 18:15-17note called "The Blessing of the Children", also in Matthew 19:13-15 and Mark 10:13-16, and in another scene Edmund Drake recites Exodus 22:18 (KJV) when he and his sister Frances are seated at the library where the murder had occurred. After the murder of Leopold Reynolds, when Poirot approaches Reverend Cottrell and Mrs. Reynolds, she recites Job 1:16bc (KJV) before leaving.
Cane Fu: Poirot stops Michael from poisoning Miranda by whacking him with his cane and having the police arrest him just in time.
Canon Foreigner: Rowena Drake was childless in the novel, but has two adult children from her late husband here: Frances and Edmund Drake.
Catapult Nightmare: Ariadne has one when she dreams of a figure wearing a jack-o'-lantern scaring her.
Composite Character: Elizabeth Whittaker combines traits of her book counterpart and Nora Ambrose, who was hinted at to be Janet White's lover in the novel.
Dies Differently in Adaptation: Beatrice White (or Janet, as she was called in the novel) was originally strangled to death by an unknown culprit. The adaptation adds some closure to her by revealing it was a suicide — this also meant changing her cause of death to drowning.
Due to the Dead: Elizabeth Whittaker hid her lover Beatrice White's suicide note so that Beatrice wouldn't be buried in an unconsecrated grave, given that at the time suicide was seen as a mortal sin.
"Eureka!" Moment: When Ariadne wakes up with a start from her nightmare, a glass bottle containing her medication smashes to the ground, causing her to remember a key detail at the party — that Rowena Drake dropped a flower vase after she saw something or someone in the library.
Flashback Effects: Flashbacks are shown with a slow shutter effect, giving them an erratic and dreamlike look.
Foreshadowing: After the morning service at church, Michael Garfield comments that he wouldn't mind being buried as compost to feed his plants. Of course, he's then later revealed to have buried someone within his garden.
Garden of Evil: Michael Garfield has an innocent-looking garden with a maze of some sort. However, this garden is not as innocent as it may seem...
Gayngst-Induced Suicide: We learn that Beatrice White and Elizabeth Whittaker were lesbian lovers, but once their relationship was found out, Beatrice drowned herself, leaving Mrs. Whittaker heartbroken and alone.
Green-Eyed Monster: Rowena Drake adds envy to her list of sins when she goes after Judith Butler after the latter is revealed to have had a child with Michael Garfield, Judith's daughter Miranda, indicating that it should have been her who was in a relationship with Michael.
History Repeats: Elizabeth Whittaker finds Leopold Reynolds' drowned body, not unlike the time she had found her lover's drowned body.
Inelegant Blubbering: Rowena Drake is reduced to this after being revealed as one of the murderers and that Michael Garfield, her paramour, would have likely disposed of her once she outlived her usefulness.
Inheritance Murder: It's implied that Rowena Drake had a hand in her aunt Mrs Llewellyn-Smythe's death — even if it was adjudged to be of natural causes — so that said aunt's estate would then pass to her. Rowena also makes sure of it by implicating Olga, her aunt's au pair, in forging the will, and killing her when Olga inevitably confronts her for it.
Ironic Nursery Tune: Children are chanting the snapdragon poem while playing snapdragon at the party. Their chant of "Snip! Snap!" echoes in the background music throughout the rest of the episode after Joyce Reynolds was murdered, and whenever a murder occurs, all the way to the end.
It's All About Me: Michael Garfield is revealed to be ultimately self-absorbed and egotistical after he confirms that he didn't really love Rowena Drake and simply used her for his own ends. Given that he was willing to kill his own daughter right before this...
Kinslaying Is a Special Kind of Evil: The murderers are shown to be especially vile due to their willingness to murder family members for their aims, including Rowena's aunt and husband as well as Michael's own daughter.
Look Both Ways: We learn that Rowena's husband, Mr. Drake, was run over by a car, which turns out was driven by none other than Michael Garfield himself (this was implied, but never confirmed in the novel).
Match Cut: Edmund and Frances burning away Hallowe'en party paraphernalia is juxtaposed with their mother Rowena burning away old correspondence.
Meaningful Echo: At the start of the episode Poirot tells George to change the radio station because he's not a fan of the custom of telling horror stories during Hallowe'en, in lieu of the Belgian custom of lighting candles in respect for the dead. At the end of the episode he tells Ariadne and Judith Butler that they should have been lighting candles for the dead, given the numerous murder victims they had sought justice for, even after Poirot himself had told a macabre story during The Summation..
Never Heard That One Before: The reason Frances Drake insists on being called "Frankie" is because of all the jokes she gets from her name being similar to that of Sir Francis Drake.
Not Now, Kiddo: People keep interrupting Joyce's attempts to tell the story of a murder she had chanced upon. It's later revealed to be not because they disregard her for being a child, but because she was disregarded because she was a Compulsive Liar.
Offing the Offspring: Michael Garfield attempts to "sacrifice" his own estranged daughter Miranda by compelling her to drink poison. Fortunately, Poirot and his team stop him in the nick of time.
Promoted to Love Interest: Downplayed with Lesley Ferrier having once dated Frances Drake. In the novel Ferrier had an affair with the Adapted Out Sandra Griffin.
Red Herring: A plot point regarding witchcraft being the cause of Joyce Reynolds' revelation of a murder turns out to be this, after two characters make allusions to the Witchfinder General, witches being tried by drowning, and the allusion to a Biblical verse from Exodus about witches, implying that Mrs Reynolds (who was religiously inclined) could have offed her own stepdaughter due to this. It turns out to be unimportant to the overall case.
Setting Update: Downplayed, as with the rest of the series the episode takes place during the 1930s as opposed to the book being set in the 1960s. It does affect a minor detail in the story, though it's not as drastic as the adaptations of Cat Among the Pigeons and Third Girl.
Sick Episode: Mrs. Oliver spends most of the episode in bed with the flu.
Spared by the Adaptation: Michael Garfield doesn't commit suicide to avoid being arrested like in the novel, and is therefore alive to personally confirm to his accomplice Rowena Drake that he never actually loved her.
Stylistic Suck: Lesley Ferrier made a deliberately mediocre forgery of the codicil of Mrs Llewellyn-Smythe's will to prevent the original version of the will being supplanted by the genuine codicil, allowing Rowena Drake to inherit her aunt's estate.
Unrelated in the Adaptation: Mrs Reynolds is the stepmother of Joyce and Leopold in this adaptation, possibly to make the murder of her entire family less heartbreaking (the oldest daughter, Ann, was Adapted Out).
Unwitting Instigator of Doom: The Reverend Cottrell's scheme to help young ladies get a job in Woodleigh Common, as well-meaning as it was, turns tragic when it results in the controversial will of Mrs Llewellyn-Smythe and the disappearance (and later confirmed murder) of her au pair.
Vader Breath: Mrs. Oliver has a dream in which she hears someone breathing unnaturally and approaching her in her bed. As soon as she hears it, she turns around to see someone in a jack-o-lantern mask before she wakes up screaming, possibly foreshadowing the fact that someone could be Michael Garfield, Miranda's dad.
Would Hurt a Child: Two (and almost three) children are killed in this episode.
