Continuity mistake: The manager knocks on the door to cabin B and the stone post in the background on the left of the screen is in direct sunlight. Two minutes of uninterrupted movie time goes by but as the Cutlers get ready to leave the stone post, and the falls behind them are no longer in direct sunlight. (00:08:00)????
Continuity mistake: Marilyn walks up to the ticket booth and gets a refund for one of the tickets to Chicago that she bought earlier in the movie. Looking at her luggage we see no marks on it at all. She picks it up the same way she puts it down, but in the next shot a large black mark appears on the front of it. (01:01:15)????
Continuity mistake: As Polly Cutler lays out on a beach chair sunning herself Ray steps back and decides to take a picture of her sitting there. Niagara Falls, which are always seen behind them are not in this shot, which has obviously been filmed on a sound stage. The bushes against the stone pillar are also different. (00:34:55)????
Continuity mistake: As Marilyn walks into room 7-A of the City Morgue to identify her husband George she's carrying her pocketbook in her right hand. After she sees the body she faints and falls to the floor but we never hear the pocketbook hit the floor because it has been neatly placed next to her before she fell. (00:42:05)????
Continuity mistake: Polly Cutler enters cabin B in order to put some Mercurochrome on George Loomis' cut hand. At first the yellow notice on the left door post is entirely in the light, then in the next shot as she walks through the door the lighting has changed and it's in the shade. (00:20:45)????