Continuity mistake: Blanc says "Where's Duke's phone?" holding his wrist in the closer angle, but his hands weren't there in the previous wider view. (01:04:05)
Plot hole: In the flashback, Whiskey fired the speargun at Helen at the bungalow away from the main house as she was fleeing at the beginning of the blackout. She has no light source with her, but somehow in the earlier showing of the events she was one of the first people to pop up at the party room seconds after the blackout started, and with a loaded speargun. (01:06:00)
Other mistake: The way Helen and Blanc clash into each other during the blackout differs radically between the first time and the lengthy flashback; in the flashback she is calling his name, and he tells her "There's great danger." Neither happened the first time we saw the scene. (01:07:00 - 01:43:20)
Continuity mistake: Throughout the conversation with Helen on Benoit Blanc's terrace, her facemask switches position between two distinct spots on the table. (01:11:00)
Continuity mistake: At the beginning of the retelling of the story, Blanc holds Helen's phone in his right hand, and yet the close-ups are of a left hand. (01:13:40)
Continuity mistake: Debriefing Helen at the restaurant the night before the impostor game begins, Blanc tells her how to behave on the boat. Her hands are off/on the table between shots. (01:18:45)
Continuity mistake: When at the restaurant Blanc says the anti-prophetic sentence "Miles Bron is not an idiot", his arms go from folded to unfolded and vice versa between shots. (01:19:25)
Continuity mistake: Andi topples the shelf and various books fall off scattering on the floor. In particular, "The Innovator's dilemma" is propped on top of a different open book. In the close-up where she pulls the napkin out of it, the book shifted without anyone touching them. (01:23:30)
Continuity mistake: When Helen shows Blanc the notepad where she drew the Clue-style tab, the letters are drawn in a different way from the close-ups (most obvious hint; the M for motive does not touch the grid). (01:24:20)
Continuity mistake: The night before the boat trip, Blanc tells Helen "This is your last chance to back out"; his forearm for just that shot is on the back of the bench. (01:24:55)
Continuity mistake: In the flashback, Helen tells Blanc as he kneels to tie the shoelace "Duke and Birdie, I think they're onto me." Notice the sunglasses poking from the top of the frame, and the right hand that moves away showing that the shades are in her left hand. But it cuts back on her in a shot from the waist up and her glasses are in the right hand. (01:25:35)
Character mistake: In the flashback, Blanc tells Helen that when Miles will pull him aside to explain his presence, that is when it will be her chance to 'snoop'. However, that piece of dialogue is just unnecessarily wrong since the whole distraction with Miles lasts just a few minutes, does not facilitate at all her snooping, and all the other guests are in their rooms just unpacking and hanging out. If anything, Miles keeping the other guests entertained and gathered together is what would facilitate her. (01:25:45)
Continuity mistake: Whiskey is walking with Helen towards the pool. When they are under a colonnade, the Taurus pendant shifted towards her left pectoral much more than it was in the previous shot. (01:26:50)
Continuity mistake: When in the flashback Claire mentions the Hindenburg, her hands go above/under the water between shots. (01:28:45)
Plot hole: The Distruptors show up at Andi's house right after the killer (Duke literally crosses paths with him) and are enraged and desperate because they can't find her. At the same time, Andi is dying from apparent suicide breathing the fumes of her car. It'd be pretty extraordinary if they were snooping around her property banging at her door and being dumbfounded for, as Claire said, one full hour, but didn't hear a car running in the garage of her small house. (01:32:25)
Continuity mistake: In the argument between Birdie and Peg that Helen happened to record, Kate Hudson's hands are in a different position in her lap in the reverse shots when she says "There's no stopping it" and just after she admits "It's my secret phone." (01:37:25)
Continuity mistake: When Helen enters by mistake Derol's room, there's no smoke visible; she leaves, and in a tighter shot on him a blunt leaves a very conspicuous trail of smoke. (01:41:00)
Plot hole: Helen looks at her phone for the first time at 9:58. From there, she quickly browses the messages everyone has been sending for several minutes to her, and does a google search. Since she gets interrupted by Whiskey and then this interruption is further interrupted by the hourly 'Dong', she must have ransacked Duke's apartment in barely a minute, which is impossibly fast. (01:41:20)
Continuity mistake: In the flashback, Daniel Craig reacts to the gunshot that fell Helen hunching in two different ways in the two separate shots. (01:44:00)
Continuity mistake: When Blanc crouches by Helen telling her that "This is our cover", she is holding the diary with both hands, but in the previous shot her left hand was on the ground, and switches again back and forth. (01:45:10)
