The Adventure of Johnnie Waverly - S1-E3
Plot hole: Forgiving the implausibility that nobody checks their own watch at the time of the kidnapping, the clock in the living room strikes 12 supposedly ten minutes early: everyone blindly storms from the room when the chimes have not yet ended, and reaches the supposed perpetrator who is by the side entrance. They talk to him briefly and the clocktower signals now the real noon. It's hard to see how 10 full minutes could have passed, and even harder when everybody runs back to the house, to find the clock there signaling 12:11: it took them a mere minute to get there, what took them so long the first time? (00:30:00 - 00:31:30)
The Adventure of Johnnie Waverly - S1-E3
Plot hole: When he is taken away from the mansion, Johnnie is hammering with his fists on the car windows, as if he was genuinely in distress and resisting the kidnapping. But as we know, that's not what is happening, he knows his captor well and came willingly. (00:31:25)
The Adventure of Johnnie Waverly - S1-E3
Plot hole: In the original story, it is made clear that Mrs. Waverly is the one in the family with the wealth, but it does not go as far as having everyone, guests included, eat plain rice and boiled potatoes, and have the mansion dilapidated with restoration work left unfinished for years. This creates several plot holes: nobody would be interested in asking lavish amounts of ransom money to people who live an impoverished life, and most importantly, the husband would never be able to justify being able to have enough money to suddenly resume construction work on the house (in the original, he simply wanted to use it as spending money).
The Adventure of Johnnie Waverly - S1-E3
Character mistake: Contrary to the short story, here Mr. Waverly consults Poirot not accompanied by his wife, and by his own initiative without even telling her at first. Given the solution of the case, this appears to be completely illogical.
The Adventure of Johnnie Waverly - S1-E3
Character mistake: When the ever gallant Poirot meets Mrs. Waverly, David Suchet hesitates for a second awkwardly as he mistakenly went for a handshake when Julia Chambers offered him a limp downturned hand instead. Not quite the kind of social faux pas Poirot would be caught into. (00:11:55)
The Adventure of Johnnie Waverly - S1-E3
Continuity mistake: When Hastings stops his car in front of the train station at the end of the episode, he talks to Poirot holding his hand on the outer circle of the steering wheel, or on the inner part in the reaction shots. (00:49:20)
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
Wblank71