Continuity mistake: Mario Adorf is walking in the hallway at the beginning, to the right, towards a large vase. The camera is on the stairs, and the vase casts a shadow to the right. In the middle shot that follows, the vase casts a shadow to the left and half of the space is taken by a shadow cast by the column that was completely absent earlier. (00:03:05)
Continuity mistake: During the introductions, Ilona Bergen exclaims; "How awesomely marvellous" with Blore casting on the wall by her a Hitchcockian-esque shadow with his profile. The shadow comes from nowhere, since the previous shot of the room lacked that and the other shadows (like the vase's) are unchanged. (00:06:25)
Continuity mistake: The butler is asked to show everyone to their room. Lombard and Ilona are looking at each other, and she has her fingertips joined as they exchange looks, but in the next shot her posture is entirely different with her arms down her sides. (00:07:30)
Continuity mistake: Lombard shows the CM suitcase to Blore; the suitcase is set on a step in the close-up, but Lombard is carrying it (and moving it around) in the previous and following shot. (00:08:00)
Continuity mistake: As soon as he gets in the privacy of his room, Dr. Armstrong takes a shot of liquor. He uncaps the bottle and puts the lid on the bed by him, and the bottle on the nightstand. When Judge Cannon barges in, the bottle on the stand is sealed. (00:08:35)
Continuity mistake: Blore is peeping on a shirtless Hugh O'Brian. You see the figurine on the mantle while Lombard approaches, and its shadow does not get into the framed nursery rhyme. In close-up, it does. (00:10:00)
Continuity mistake: At dinner, the doctor is having a glass of water. Blore comments "Ahh, keeps the old hands steady, eh?" Miss Bergen has already put down the glass of wine, but she's on the contrary holding it in the next shot. (00:12:15)
Continuity mistake: Judge Cannon proposes a toast; the empty chair at the head of the table is shown; besides a blatant different in lighting (look at the shadows cast by the Indians tray, and Mario Adorf going from having his hands in the shade to perfectly visible), there is a wine glass by the tray, and Judge Cannon is holding his. (00:12:25)
Continuity mistake: Lombard responds to the toast with a grin, saying "I hope Mr. Owen isn't lost in the snowstorm." He starts the toast in that shot picking his glass from the table like everyone else, but in the previous he already was holding it, in his lap. (00:12:30)
Continuity mistake: When Fabian murders the 10 Little Indians nursery rhymes at the piano, the sheets on the instruments are positioned differently depending on the camera angle - easy to notice when Grohmann brings him a new drink; the sheets are all straight, while when his wife picked up the coffee cup one sheet was askew sticking out with a corner. (00:13:45)
Continuity mistake: Once Fabian is done with his performance, General Mandrake heckles him. The cigarette in his holder is practically spent, but it was whole when the 'singer' was already down to the last little Indian. (00:15:00)
Continuity mistake: When the General mentions Mike Raven's "infernal noise", the Judge is looking ahead at him. He is pensive and with a hand to his chin when the shot changes and Owen begins to speak. (00:15:05)
Continuity mistake: Owen mentions that he's charging the guests with crimes. Cut, and you can see that there's terrible continuity; Ilona Bergen and the doctor have entirely different posture and arm position, the hands of the judge are close instead of far apart, but even more conspicuously, Frau Grohmann was facing the guests, now is facing the wall. (00:15:20)
Continuity mistake: Mike Raven performs the song with his collar unbuttoned and bow tie loose. He also dies the same way. In between though, there's the scene where everyone is in the record player room. Everyone but him, who can be seen sitting at the piano. With the bow tie properly fastened like the other guests. (00:17:50)
Continuity mistake: When Blore gives his explanation about his presence at the villa, marked shadows appear on the mantle where no shadow was present before. (00:19:50)
Continuity mistake: The decanter is open when the singer mentions the "10 little skeletons", and its glass lid is on the top of the piano. When he takes the fatal sip and dies, the decanter is on the keys, but the lid is in a different spot. (00:20:50 - 00:22:00)
Continuity mistake: When the doctor reaches for the glass, he is about to catch it cupping it with two fingers on each side of the stem. He freezes due to Blore's admonition, but his hand is now about to grab it by the side. (00:26:10)
Continuity mistake: Ann Clyde and Hugh Lombard are drinking milking in the kitchen. During the whole scene Shirley Eaton's golden hair is behind or in front of her shoulders, it keeps switching. (00:28:30)
Continuity mistake: General Mandrake confesses his crime. Ilona Bergen asks "How does this help?" Lombard is standing straight and tall, but in the previous shot he was leaning at an angle against the wall and the drawer. (00:32:40)
Continuity mistake: After the General takes a weight off his conscience admitting to his guilt, his handkerchief feels lifted too and sticks out of his pocket more than before. (00:32:45)
