Continuity mistake: Hastings and Poirot are talking about the optimist friend. Once Hastings says "It bucketed down", he's holding the newspaper, and it stays pretty firm. Miss Lemon knocks, and the newspaper is now folding at the upper corner. (00:06:45)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: About the burnt will, the lawyer asks the obvious question to John Cavendish "Are you so sure it's a coincidence?" He's holding in his raised left hand a sheet. Next shot and he has both hands down on the desk. (00:48:55)
How Does Your Garden Grow? - S3-E2
Factual error: At the very beginning of the episode, Katrina visits the Soviet embassy. It is written in big letters; "Union of the Soviet Socialist Republic", while the correct official name was "Union of Soviet Socialist Republics." (00:01:45)
Revealing mistake: When Japp points at the news on the paper about the mine stocks going up, in the close-up you can see easily that only the title and the enlarged text of the first 3 lines talk about the mine. The rest is sports talk. (00:33:55)
How Does Your Garden Grow? - S3-E2
Continuity mistake: Once Japp passes him back the seed packet telling him it's empty, Poirot checks it out; in the close-up he's holding the paper in a completely different way (the side instead of the top). (00:11:20)
Wasps' Nest - S3-E5
Continuity mistake: Poirot is examining the photos taken by Hastings at the party. Depending on the camera angle, the pictures and their reciprocal distance change across the whole sequence. (00:15:30 - 00:16:05)
How Does Your Garden Grow? - S3-E2
Continuity mistake: Miss Barrowby pretends to have just then recognized Poirot, she lowers her left hand, but has it up when he nods to her, and he has his matching hand suddenly higher too. (00:09:00)
The Million Dollar Bond Robbery - S3-E3
Continuity mistake: When Poirot receives his platter of buttered brains, the delicacy that makes Hastings queasy is turned a different way in each shot (easy to tell from the asparagus). (00:28:05)
Wasps' Nest - S3-E5
Continuity mistake: Having received Japp's phone call, Poirot puts down the picture of the mysterious man. The photo sits on top of the other pictures in a different spot at the cut. (00:35:35)
Wasps' Nest - S3-E5
Factual error: When John Harrison check out of the organizer, the days of the week are wrong for a 1935 setting (September 24th is a Monday, etc), looks like a 1934 one. (00:12:00)
The Million Dollar Bond Robbery - S3-E3
Continuity mistake: When Poirot says "I'm sorry" to the culprit, he has the hand on the shoulder of his accomplice. Her hair is on and off that shoulder in a blink. (00:48:35)
The Million Dollar Bond Robbery - S3-E3
Continuity mistake: After Ridgeway puts down his Queens High, his hand is hovering slightly on the table, but at the cut it is arched, fingers pointing on the table. (00:28:55)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: Cynthia is sobbing with Hastings, and he asks her to marry him. The handkerchief in her hand changes position between shots (particularly easy to spot when you look at the black band). (01:13:05)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: After Hastings reminds him of the mantelpiece, Poirot shouts "Mon Dieu!" and pounds the table. The cards scattered on the table differ in disposition between shots when he stands. (01:21:05)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: When Hastings spots Poirot from the window as he arrives for the denouement, his hand is in a different position on the window frame (left or right of the vertical bar). (01:26:55)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: At the hearings, the doctor is on the stand and says "There was no strychnine in it." Mr. Wells closes his fountain pen. But then in the next shot he holds it in his hand. (00:52:40)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: Poirot locks the document case in a close-up. The shadow on the case is at the center of the object, but in the wider shot it is projected entirely on the left side. (00:38:15)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: Mrs. Inglethorp's death happens with her having a much messier hair and the neck tilted to an angle in the wider shot, compared to the close-up on Gillian Barge. (00:30:00)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: When Hastings tries the fake beard on, it sticks past his fingertips more in the shots from behind than on the front. (01:09:15)
The Mysterious Affair at Styles - S3-E1
Continuity mistake: The larger broken porcelain pieces Poirot is examining in front of the fireplace change place between shots. (00:39:45)
