Continuity mistake: In the bell tower the shadow is at about 45 degrees, but when Marilyn walks there the sun is overhead. (01:03:10 - 01:05:40)
Continuity mistake: The boat keeper throws his newspaper onto the ground as he runs to the boat that George Loomis is stealing. Later when Ray Cutler runs past that spot the newspaper is now on the chair. (01:16:25 - 01:17:15)
Continuity mistake: Both Marilyn and Jean's faces are dry as bones in the scene below Niagara Falls but Marilyn's lover is drenched. (00:13:50)
Continuity mistake: George Loomis gets the engine of the Myra III running then proceeds to untie the two ropes from the dock leaving them dangling off the side of it. In the next shot as the boat sails away we see no ropes. (01:16:30)
Continuity mistake: As the Canadian motorcycle police drive away George Loomis hides across the street behind a boat and some items that look like they belong in a tag sale. In the next shot as he walks away all of the items on the right of the boat have been rearranged. (01:13:10)
Continuity mistake: As Polly and George Loomis are rushing down the middle of the Niagara River a tree appears above Polly's head on the back of the boat. (01:23:10)
Continuity mistake: Ray Cutler decides they should leave the Rainbow Cabins and picks up one of two stacks of books on a table to the right of the front door as he talks to Polly. No one goes near this spot but earlier in the scene there was only one stack of books along with a pocketbook (which is now on the floor) on the table. (00:49:45)
Continuity mistake: At night the Rainbow Cabins has a little outdoor party. The Cutlers are dancing together, and when the song stops Ray has his arms around Polly's shoulders. In the next shot his arms are around her waist. (00:16:35)
Continuity mistake: At the bottom of the Scenic Tunnel Tour, Polly runs into Marilyn kissing her lover. At first the gentleman has his hands around her waist. Then in the next shot his right hand is holding her face. (00:13:45)
Continuity mistake: In the first scene of the movie Marilyn is in bed smoking a cigarette and the shadow of the light coming through the Venetian blinds goes across the sheets from left to right. She hears George coming into the room, puts out the cigarette and in the next shot the shadow from the blinds has been rotated 90 degrees and is now extending from the foot of the bed to the head board. (00:03:20)
Continuity mistake: Polly Cutler enters cabin B in order to put some Mercurochrome on George Loomis' cut and the do not disturb sign on the door knob is tilted to the left. No one goes near it but later in the scene it's been set straight. (00:22:55)
Continuity mistake: The manager knocks on the door to cabin B and Marilyn comes walking out. The shades to her right are closed but two shots later they're opened. (00:08:25)
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: George Loomis goes over to the front door and shuts the light so that Polly Cutler can see the falls in the dark. The blinds on the left of the door are half open but when we see them again later in the scene, they're fully open even though no one has gone near them. (00:24:05)
Continuity mistake: The gash on Lomas' head changes between scenes. (01:16:15)
Continuity mistake: At the Rainbow Cabins, Polly Cutler speaks to the Kettering's and holds a bouquet throughout the scene, and it keeps changing positions between shots. (00:45:05)
Continuity mistake: Polly decides to take a nap in cabin B and the ash tray on the night table moves to the edge during the scene without her going near it. (00:46:45)
Continuity mistake: Marilyn speaks to the cabin manager and says, "It's the first good sleep he's had in over a week" and the fur on her collar is motionless. In the next shot the wind is blowing it continuously. (00:08:30)
Continuity mistake: Marilyn's shadow falls on the door as she speaks to Mr. Qua and the Cutlers, and after finishing she goes back into her room. In the next shot the lighting has changed and Mr. Qua's shadow falls in the opposite direction onto the Cutlers as he speaks to them. (00:09:30)
Continuity mistake: Mr. Qua is watering the flowers and as Polly Cutler speaks to the Kettering's we see the front of the car and there's no water on the gravel by the tire. After they get into the car and drive away in the next shot, there's a lot of water on the gravel. (00:45:15)
