Plot hole: The hole in the hat was pre-existing and the bullet was fired in advance and dropped. Poirot notices immediately the hole when Nick puts the hat down but somehow missed it while she was wearing it as she supported him. He also does not notice that the bullet has not been fired at that time - which would have been still hot if just fired, not at all if dropped. Most importantly, in the spot where they were sitting, it's not even possible to think where a shooter could have ever been hidden; nobody wonders where the mysterious shooter could have been or cares to investigate the circumstance despite knowing the very moment the supposed shot happened. The fact is basically ignored throughout the rest of the episode.
Audio problem: There's a bit of a mix-up in the codenames of the cars who chase Reggie Dyer. Unit 7 is the first to give chase and it is identified by its crew with the photographer. Then Unit 8 intercepts at the rendez-vous point. Check the license plate; FVW 49. Japp mentions a "unit 10" that is not shown. Later in Chinatown, Japp calls for the other cars, and "Car 8" responds, but its license plate is now YD 8501 and it's another car model. Unit 10 is again not shown. They dubbed in the wrong voiceover, they should have kept offscreen the second response by Unit 8 and made it Unit 10's.
Factual error: In Poirot's study, Lord Pearson shows the big piece of mineral, saying "You're left holding a a nugget of top-grade 24-carat silver." That's a laughable blunder, from a top level banker and investor about to do a massive mining deal even. Silver purity is expressed in millesimal fineness. (00:11:30)
Factual error: The episode is set at a precise date (it's even a plot point); 8/2/1935. But at the beginning Poirot and Hastings are playing Monopoly, and right there on the board you can distinctly read; "Trade Mark - Pat.app. For Nº 3796-36." As signaled by the last 2 digits, it's a 1936 edition (the UK localization of the game). (00:01:40)
Character mistake: In the hotel lobby, Poirot, indignant of Hastings' attitude towards the murder case, says "After three attempts had been made at the life of M. Nick, Poirot gave his word he would protect her." But he did that after four attempts; Nick already avoided 3 "mysterious accidents" (painting, car, boulder) and Poirot witnessed the 4th, the bullet that pulled him into the whole case to begin with. (01:02:20)
The Adventure of the Western Star - S2-E9
Character mistake: While handing Mademoiselle Marvelle's letters to Hastings, Poirot calls him "Chief Inspector". (00:06:55)
Plot hole: When Poirot and Hastings break into the house, they search the entire house for the box, without success. However, later on, when they are in the kitchen, the housekeeper comes down the stairs - having been lying in wait for them. How did Poirot not run into her when he was initially searching upstairs, particularly when he was making such a thorough search?
The Adventure of the Western Star - S2-E9
Revealing mistake: Japp is waiting for Van Braks to make his move, and when he is hopping on a taxi for the airport, he begins to tail him. When the car moves, reflected in the door is a modern No Parking cone in bright yellow (incidentally, they also pass by a parked car with a FUU 692 plate that is a bit too recent for the series, being an Austin Big 7, first produced in 1937). (00:41:05)
The Adventure of the Western Star - S2-E9
Factual error: Assuming the episode is in line with the others of the season and it is set in 1935, a few vehicles shown are slightly too recent. The plane waiting for South Africa is a Beechcraft Model 18 (first produced in 1937), the train going to Yardly has a SR Q locomotor first produced in 1938, and the truck that slows Japp down before getting to the airport is a Bedford M-Type, a model first produced in 1939 (the specific one used in this episode is from 1947).
The Adventure of the Western Star - S2-E9
Continuity mistake: When Poirot enters the room of Mademoiselle Marvelle after her husband took off for the airport, she opens the door to him holding the door in two contrasting ways (right hand on the side of the door in the first shot, behind the door using the left hand to push it closed in the other). (00:41:35)
The Kidnapped Prime Minister - S2-E8
Factual error: The calendar behind Japp in Scotland Yard places November 13 as a Tuesday, but that is wrong for 1935, when the story is set (the whole season consistently goes with 1935 historical facts, Poirot in this episode makes a reference to "the Dutch", and the newspaper page Hastings shows up with at the end of the episode talks about the notorious gangster's death, happened that year). It was a Wednesday in 1935, to be Tuesday it should have been 1934. (00:34:00)
The Kidnapped Prime Minister - S2-E8
Factual error: At the end of the episode, during the fitting of the jacket with monsieur Fingler (last role of character actor Milo Sperber), Hastings is reading a newspaper prop sporting a doctored first page (the real headline, which was about Italy, is replaced by the fake PM speech) of The Daily Express based on the real Friday October 25th, 1935, which is wrong in month and day of the week (the appointment was on Thursday and it's supposed to be November going by the various calendars seen throughout the episode). (00:51:00)
The Kidnapped Prime Minister - S2-E8
Factual error: Poirot in this episode has to save the Prime Minister, kidnapped before he could attend the League of Nations Disarmament Conference. This episode is set in November (the previous of the season in October), but it can't possibly be 1935, since the Disarmament conference happened between 1932 and 1934. It makes mention of the PM being vital to have at least a chance at preventing Germany's rearmament, with Hitler withdrawing Germany from conference and League of Nations entirely in October 1933. It should be noted though that the conference happened in Geneva and not in Paris like it's described here. The original material did not have this sort of inconsistency since it was set to happen much earlier in the century and for the Treaty of Versailles, where Paris would have been the correct destination. Both short story and adaptation have as prime minister a fictional "David MacAdam", with him designed to be a stand-in for David Lloyd George, just recently replaced as PM.
The Adventure of the Cheap Flat - S2-E7
Plot hole: The professional hitman from the US does not have a gun of his own, and does not bother in the long time elapsed between the apartment's hit and the nightclub (it could even be hours) to check if the gun he just grabbed is loaded or not. Who in the world would not take a split second of his time to peek at the cylinder and see how many bullets does he have? An assassin planning to kill with that gun, even.
The Adventure of the Cheap Flat - S2-E7
Factual error: Agent Burt brushes off Poirot's question saying "When will you guys understand there is no such thing as the Mafia, the Black Hand or the Cosa Nostra?" The last term he uses, while not impossible (since members of the organization were indeed referring to it as such) is a huge improbability, considering that officially FBI (and certainly the general public Burt is lashing at) came to know the real name (adapted in "La cosa nostra") only decades later with the Valachi investigations. (00:24:05)
The Adventure of the Cheap Flat - S2-E7
Factual error: When Poirot asks O'Brian about unsolved crimes with young couples as suspects, he says "There's that Bonnie and Clyde of course, but they're at large somewhere in the American Midwest", to which Poirot replies "And let us hope that is where they remain." Bonnie and Clyde were killed in Louisiana on May 23, 1934. The episode is set in October 1935. (00:12:20)
The Adventure of the Cheap Flat - S2-E7
Continuity mistake: During the party, the establishing shot shows everyone in the small circle Poirot is a part of having a glass of champagne. That includes Mr. Robinson. As Poirot puts on the tray his own glass, someone's hand reaches over for another - it can only be Mr. Robinson's, as his wife is wearing gloves, but he never put down his own glass. (00:06:05)
The Adventure of the Cheap Flat - S2-E7
Continuity mistake: Hastings, Japp (for some reason) and Poirot are at the movies; when the camera pans through the room, there's a guy sitting behind Hastings, while behind Poirot there are a red haired woman and a man, as confirmed by the close-ups. When the music stops and Hastings tells Poirot that he can open his eyes, the couple have moved behind Hastings. (00:02:50)
Double Sin - S2-E6
Continuity mistake: When Hastings storms out of the antique store claiming to have solved the case, Poirot follows him until he turns into an alley. In the view from the back of the alley, there's a man with a hat who walks all the way past Poirot and turns the corner into the main road. In the reverse angle, the guy is still walking down the alley in front of Poirot. (00:42:30)
Double Sin - S2-E6
Continuity mistake: Madame Durrant is showing the niece the medallions she is supposed to sell. In close-up you can see her holding the suspension ring with her right hand, and her left hand too, on the side, with the thumb on it. But in the wider shot, she is using merely the side and back of the left hand for support, the thumb being at distance from the jewel. (00:08:20)
