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: 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 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: 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: 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: 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: 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: 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: 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: 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: 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)
Plot hole: Lombard is able to deduce that the doctor died hours before because there are no footprints around him, canceled by the snow that fell through the night. If that's so, then the doctor himself should have a considerable quantity of snow on his back and hair, and instead he has none. (01:22:40)
Other mistake: Lombard supposedly just pretended to drop the key inside the chandelier while he palmed it instead, but A) you can see the shadow of the key in the glass bowl and B) the noise comes with a timing and pitch that could be explained only by a key dropped, not banged against the rim. (01:11:05)
