Continuity mistake: Poirot meets Hastings about to go play golf with a Stiffie. Hastings holds his hat by the brim, which turns into the crown in the reverse shot. (01:02:05)
Continuity mistake: Commander Challenger in front of his boat laughs with Hastings "I hope my alibi is in order." As he says that, Hastings nods. During this close-up, his hat is casting a completely different shadow, covering his whole shoulder instead of just the back of the neck as in the rest of the scene. (01:03:35)
Continuity mistake: When Japp talks to Poirot and Hastings about the gallery troubles, the peppermint rock candy he is waving is wrapped differently between shots. (01:13:40)
Continuity mistake: Starting the seance, Poirot ask everyone to hold their hands. Lazarus barely stifles a laughter. Between that shot and the previous, his hand goes from above the table to underneath it. (01:38:25)
Continuity mistake: At the beginning of the opening credits, there is a close-up of the model boat pushed forward. It passes by a kid who is hunched over, hands on his thighs. Wider shot, and the kid just watches the sailboat pass by standing apathetically. (00:02:15)
Continuity mistake: Sitting on the park bench, Japp narrates the jewelry heist to Poirot. The passersby during the scene change in the various angles, and the most evident demonstration is offered by the fella that starts his walk exactly when Japp sits down. Grey pants, a sleeveless vest and hat, he walks all the way to the path in the background and exits stage right. But he's walking behind Japp when he says "The stones in his pocket were not the real stones." (00:03:00 - 00:03:45)
Continuity mistake: When Poirot and Hastings enter the Athena, there's an establishing shot as they walk to the right of the concierge. In the following shot, some elements like the lady with the flower dress by them are consistent, but the desk employee is suddenly on the phone and a bellboy appears by the stairs. Also the lady in the corner changes from a blonde to an elderly woman in a red coat. (00:05:50)
Continuity mistake: Poirot tells Miss Lemon to calm down because "It is only the simple blackmailer." Pauline Moran has her right hand on the bag, but in the close-up that follows her hand is at a distance from it. The difference in position (and thus in the takes being edited together) is reflected by a mistake happening a few seconds later, when you can notice as she turns around to answer the door, that her gloves have also switched hand. (00:12:10)
Continuity mistake: Lavington puts his hat on the couch before talking to Poirot. The hat shifts closer to Hastings and then back closer to the armrest during the scene. (00:12:45 - 00:14:30)
Continuity mistake: Lavington arrogantly sits in Poirot's study and opens his cigarette case, closing it after. In the following close-up, the case is open again. (00:13:15)
Continuity mistake: When not-so-Lavington is spying Japp and Mad Dog Poirot outside of the station, he is holding the wheel with his right hand at the top, but a moment after he's using that hand to smoke instead. (00:34:35)
Continuity mistake: When the box opens revealing the jewelry, the jewelry is scattered differently each time it is seen. The box itself gets closer to the table's edge when the lady nabs the jewelry. (00:40:40 - 00:42:40)
Continuity mistake: When Gertie and Joey make their escape running down the stairs of the hall, they pass by a couple (she has a white hat and a blue dress). When Poirot and Japp run after them, the same couple has jumped back several meters. (00:43:00)
Continuity mistake: The cream colored shoes of the Lady are prominently featured in the finale. When the actress has to run, not only are the heels replaced by modern tennis shoes, but they're black, in contrast with her white stockings. (00:46:40)
Continuity mistake: His Bankship visits Poirot during the evening, and begins telling him the story of the silver mine. "For half a century, men have died", he says. Poirot has the magnifying lens in the right hand, but also the rock in the left; cut to a different angle, the hand with the rock is held low, out of frame, and then back to the first shot, with the rock exactly where it was. (00:11:55)
Continuity mistake: Poirot opens the "intolerable" letter Miss Lemon hands him; camera in the door and he has his finger between envelope and letter, reverse shot and he is holding them parallel together. (00:33:45)
Continuity mistake: Poirot reads the telegram after the opium den raid. The letter is in his left hand, but moves between shots to the right hand. (00:40:40)
Continuity mistake: Mrs Pengelley is outraged by Hastings' question about the niece. Poirot opens his umbrella and begins to move forward to ask a different question. The left side of his coat is mostly spotless, but in the next close-up that side is instead covered in water stains, including a quite visible streak on the chest. (00:05:40)
Continuity mistake: After reading the will of the deceased, the lawyer folds back the first page twice in two different shots. (00:26:05)
Continuity mistake: Hastings sits down when Japp is having his meal at the inn, and eats one of Japp's sandwiches. In the rest of the scene, the sandwiches on the plate change position and Japp's beer has been replenished a bit. (00:35:00)
