Continuity mistake: Just before Poirot moves to the other side of the dinner table after revealing lady Westholme's deception, Dr. King at first has both hands on the table, but in the next shot she is in a different position. Same for Jefferson Cope and his cigarette; he's smoking, then he is not. (01:33:55)
Continuity mistake: Lady Westholme is cross with Poirot and making her exit from the office she leaves her leather folder behind. Look at its position on the table; Miss Quinton fetches the bag on her way out, and it is placed differently, as made evident by the way it sticks out of the table. (00:58:35)
Continuity mistake: Poirot is with Lady Westholme and Miss Quinton at the Royal Commission. A man from the staff opens the door, and Miss Quinton turns all the way to look. He announces a phone call, and the reaction shot on the ladies begins with the woman turning around again. (00:56:25)
Continuity mistake: In Lady Westholme's flashback, she asks Emily if there's anything she and Miss Quinton can do. From the front, the table and the woman's lap are in the shade, but in the reverse shot they are fully sunlit, and back with no sun when she watches them leave. (00:56:00)
Continuity mistake: Inside Lord Peel's study, Poirot asks Lady Westholme what did she do after lunch, since "You did not immediately go for your walk, I believe." Peter Ustinov poses the question with his hands behind his back, but Lauren Bacall's answer answers with the stand-in for Ustinov posing with his hand on his hip. (00:54:40)
Continuity mistake: When Ray tells lady Westholme that his mother would like a word with her, the position of the folders in her hands change. (00:41:40)
Continuity mistake: During the coronation ball, Poirot explains that the murder must have not been intimate enough with the victim to tamper with the heart tonic. As he says that, his pince-nez are on his lap, but they are in his breast pocket a moment later, and it switches position again when it gets back to the same camera angle. (01:29:30)
Continuity mistake: When Lennox picks the wristwatch from his mother's lap showing the actual events, the natural light of the scene is entirely different between shots - the skirt is sunlit in close-up, in the shade in the other angle. (01:25:45)
Continuity mistake: When Nadine gets up from the chair to confront Poirot about implicating young Ginevra, she puts in a haste her shawl on the plate in front of her, but it's perfectly rolled in during the rest of the scene except another shot. (01:23:35)
Continuity mistake: Poirot runs through the hypothesis that Carol murdered her stepmother. In the middle of it there's a close-up on Miss Quinton smoking a cigarette, but in the wide shot immediately following that, she isn't. (01:21:10)
Continuity mistake: When Poirot in his teatime speech addresses Raymond Boynton, there's a close-up on Dr. Sarah King looking at Poirot defiantly. There's no direct sunlight on her, but then there she is, sitting next to Raymond with sun all over the chest and left shoulder and cheek. (01:19:50)
Continuity mistake: At the denouement during afternoon tea, Poirot opens his statement greeting "Ladies and gentlemen." Look at Lady Westholme's table; she and Miss Quinton in the wide shot turn towards Poirot to listen, but in the next shot they are in an entirely different position (Lauren Bacall has her hand under her chin, then on the table, Hayley Mills puts her hand in her lap, then she has her forearm on the back of the chair). (01:19:10)
Continuity mistake: When Dr. King drops the gun, in close-up it bounces on the back of the thigh of the victim, but in the previous shot she tossed it nowhere near that spot. (01:16:55)
Continuity mistake: On the final day of the mystery, Doctor King apologizes to Poirot at the concierge. Poirot's reading glasses are located in his pocket, towards the left or center, as we can tell by the straps. When the two are coming out of the hotel, the glasses shifted to the right corner of the pocket. (01:14:40)
Continuity mistake: Carbury brings Poirot the report with the results of the questioning of the various "Arab boys." Poirot sets it on the counter of the hotel's bar. The colonel does not touch it until later, when he does it's turned differently. (01:13:00 - 01:13:25)
Continuity mistake: After the spider scene, colonel Carbury and a certain Captain Rogers (not that one) approach Poirot; suddenly at the entrance behind them there are people who weren't there a moment before. (01:12:35)
Continuity mistake: In the cave, Raymond turns his back to Poirot casually saying that his mother was "pretty upset." Notice the sweater he threw on over the shoulder. Cut to a couple seconds-long flashback with his mom hilariously overreacting, and when we see him again the sweater is on his shoulder in a completely different way, as you can see from the decorations. (01:09:55)
Continuity mistake: Poirot and colonel Carbury are going up a flight of stairs when the Belgian poses to his positively baffled friend a few questions. Before the camera cuts the first time, Carbury takes in his right hand the baton he was carrying under the left armpit, but in the next shot it's back exactly where it was. (01:06:10)
Continuity mistake: Poirot is at the hotel's reception, phone in hand, and spots Cope trying to leave. The whole counter in front of Poirot shows direct sunlight on it, but in the conversation the light of the set is entirely different and most of the counter except a couple of narrow spots is in the shade. (01:03:55)
Continuity mistake: When Poirot takes notes during Carrie Fisher's interview, his panama hat is at a different angle in the close-up of his writing hand than it is in the wider angle. (01:02:05)
