Wasps' Nest - S3-E5
Factual error: When John Harrison check out of the organizer, the days of the week are wrong for a 1935 setting (September 24th is a Monday, etc), looks like a 1934 one. (00:12:00)
The Tragedy at Marsdon Manor - S3-E6
Factual error: It is well established that the episode takes place in 1935 (Nairobi Daily Press dated Saturday July 27 1935, the poster in town advertises the meeting for "Today, Wednesday September 4th", day of the week consistent with the year), but Poirot and Hastings are stopped on their way to the train station by a Wolseley Series II - 14/56, a model that entered production in mid 1936. (00:17:00)
Factual error: Attention to detail in props is always extremely high in this series, and tubular flashlights have been in circulation since the beginning of the century. However the one that the supposed burglar is holding as they make their way through the top floor of the villa looks perfectly modern and unlike any model compatible with the 30s. (00:10:20)
Factual error: Hastings and Miss Lemon decide to investigate on their own. In the outside view of the first suspect they go question, a large contrail is visible on the left of his building (contrails were not a complete impossibility in the 30s, but it's rather odd to randomly see one in an establishing shot for this timeframe). (00:22:40)
Factual error: Poirot is visiting an art exhibition with the Countess, and expresses his admiration for a painting by Marc Chagall. Amazingly enough, that painting is "Les Plumes en Fleurs", something Chagall will create in 1943, years after the time when this pre-WW2 episode takes place. (00:24:50)
Factual error: At the party, Marcus Hardman tells Bernard that the Countess recently arrived from Russia, and she describes herself as being in exile. Which made sense in the source material, set right after the Russian Revolution, but less sense in this adaptation, set in the mid 1930s. If she stayed in Russia that long, she would have spent 15-20 years with zero privileges from her rank at that point, and nothing from her old wealth, seized by the communist government.
The Adventure of the Egyptian Tomb - S5-E1
Factual error: In the scene after Poirot pretends to be poisoned, a person folds the modern flag of the Arab Republic of Egypt instead the flag of the Kingdom of Egypt as it was at that time.
The Underdog - S5-E2
Factual error: Lily looks over part of the procedure for the manufacture of Astroprene. There are several problems with the chemical structures shown in step two of the procedure. This step appears to be a simple acid catalyzed rearrangement of the molecule shown. The procedure should begin with a C inside the hexagonal ring and end with the C outside the ring with no other changes. The errors include, among other things, a carbon atom at the lower left of the ring with two lines (bonds) to it. The C should have four bonds (lines), the two shown plus two to hydrogen atoms (H). The bonds to H may be condensed so the C will look something like -CH2 - (the 2 would be a subscript). (00:10:30)
Factual error: Poirot smells and very carefully tastes a drink and says, "Potassium cyanide." It is impossible to distinguish between potassium cyanide and sodium cyanide (the other common cyanide) by this method. In addition, there are another less common cyanides that would smell and taste the same as potassium cyanide. (00:16:01)
Factual error: The Jarrow crusade was 5-31 Oct 1936. The sign posted at the hostel stated Poirot was speaking 5 April. (00:15:30)
Factual error: Poirot gets on the train to London. The engine has an SNCF plaque on it. The video then cuts to the 1936 cycle race. The BCNF was not formed until 1938.
Factual error: The prologue shows the dubbing of a newsreel by a narrator. Ten years later it's 1936. But in 1926 Hollywood was still experimenting with sound film, and a UK news reel would've been silent. (It was 1929 before any sound films were made in Europe).
Dumb Witness - S6-E4
Factual error: Spoiler. Police Sergeant Keeley tells Poirot that Doctor Grainger died of carbon monoxide poisoning. The killer turned the natural gas in the bedroom and did not light the heater. This would result in the room filling with natural gas, not carbon monoxide. (01:17:30)
Suggested correction: Surely it was coal gas at that time, before we all converted to natural gas?
The product of coal gas is still methane, which is CH4. It may contain tiny volumes of CO but the gas asphyxiation would still have come from methane, not carbon monoxide.
The Murder of Roger Ackroyd - S7-E1
Factual error: A few drops of acid are dropped on a penny and the liquid bubbles (colorless liquid) as the acid eats its way through the penny. The penny is mostly copper. Any acid that can react with a copper will also produce a bright green to bright blue solution of dissolved copper, which is not the color seen. (00:05:20)
Suggested correction: Not necessarily. It depends on the acid and its strength. A weak acid may only oxidise copper to a monovalent state (Copper (I)) (which is colourless) rather than its divalent (Copper (II)) state which produces the blue solution.
Factual error: In the beginning of the episode when Poirot eats with the daughter of the murdered man, on several occasions there are closeups of him. When in closeup, it is obvious the actor is wearing modern contact lenses, not accurate for the time.
Factual error: The night of the murder, before Jackie has her nervous outburst Ferguson is reading a magazine. It's Life magazine from January 1937 with FDR on the cover. The episode is set in January 1936 (as you can see from the date on Pennington's ticket).
Factual error: When Jacqueline surprises the Doyles revealing her presence on the boat, she was initially covering her face with the December 1938 issue of Vogue. The story is set in January 1936.
