Plot hole: Since the Countess was the only person to be at every dinner when the jewelry thief was in action, it takes a very special kind of idiot to not identify her as the culprit. Japp here did not need at all Poirot's acumen, but simple due diligence cross-checking the guest lists, something there is absolutely no reason he wouldn't do, and yet she is never treated as a special suspect. Also, Japp's job is described as being in jeopardy after the first 3 thefts, a 4th happens, he does not quite solve it (but retrieves at least the necklace), but he's off the hook despite the thief being unidentified, at large and with still the jewelry stolen from the first 3.
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Agatha Christie's Poirot (1989)
1 plot hole in The Double Clue - chronological order
Starring: David Suchet, Hugh Fraser, Philip Jackson, Pauline Moran
The Mysterious Affair at Styles - S3-E1
Plot hole: Can't fault this massive plot hole to the adaptation, but to the source material; the culprit (forgetting the stupidity of writing an incriminating letter detailing the plan to murder someone, and put it in a desk he shares with her) since there are people outside the room that are about to enter, tears the letter in 3 neat vertical strips, rolls them, puts them in the vase on the mantlepiece, and then opens the side door to slip away...instead of simply pocketing the letter and going through that same door. Nobody was going to search him or anything and could have burned it, torn it into confetti, anything, later. It takes way way longer to do what he did, which needed him to stay there in the room increasing the chances of being found out. And of course he and his accomplice do not retrieve the letter after.
The Disappearance of Mr. Davenheim - S2-E5
Hercule Poirot: And please, do not fraternize with that creature. I am still training him.
Captain Hastings: It's only a parrot.
Hercule Poirot: I was talking to the parrot. (00:27:00)
The Disappearance of Mr. Davenheim - S2-E5
Trivia: David Suchet performed all the various conjuring tricks Poirot is trying to pull off. The illusionist in the theater show at the beginning is the late Patrick Page, real life stage magician and coach/consultant for the episode.
The Murder of Roger Ackroyd - S7-E1
Question: The doctor (James) put on a Dictaphone to make the suggestion that Roger Ackroyd was alive at 21:30 hrs. But how could he know that someone (Paton) would pass the door of Ackroyd's study at precisely that moment?
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