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Continuity mistake: Mr. Qua and the Cutlers walk away from the Loomis' room after talking to Marilyn. If you look closely the stonewall to the left of them is not in direct sunlight as it was a few shots earlier when they walked up to the door. (00:09:45)

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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)

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Continuity mistake: George Loomis goes over the falls and Polly is safely on an island in the middle of the river with green trees on it. Several shots later the trees are purple. (01:26:35)

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Continuity mistake: Polly is safely on an island in the middle of the river as we see the helicopter coming to rescue her. Unfortunately when we see her they're showing us the falls from the wrong direction and we can see the island she's supposed to be on behind her. (01:26:35)

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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)

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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)

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Continuity mistake: As George Loomis tries to steal the boat there's an ice bucket underneath the table to the right of the steering wheel. Later Polly comes back with some beer and grabs for the ice bucket, which has been rotated 45 degrees even though no one went near it. (01:15:35)

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Continuity mistake: George Loomis tries to steal the boat and pulls the ignition wires straight out from under the lock. No one touches them but the next time we see them they're hanging differently. (01:14:55 - 01:16:10)

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Continuity mistake: Inspector Starkey gets into the police car before Ray Cutler, who sits in the rear driver side seat as they pull away. Several shots later we see them again in a close-up chasing George Loomis and their positions in the rear of the police car have reversed. (01:20:50)

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Continuity mistake: George Loomis strangles Marilyn who falls to the floor of in the bell tower holding a yellow scarf near her face. In the next shot it's held away from her body. (01:06:25)

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Continuity mistake: Two Canadian motorcycle police drive up and speak to the boat keeper about George Loomis, and a prominent tire mark is on the side of the road in front of the black car. The next time we see this spot as Ray and Mr. Kettering run to the boat it's not there. (01:12:20 - 01:17:10)

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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)

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Continuity mistake: Before George Loomis strangles Marilyn in the bell tower she knocks everything out of her pocketbook looking for a dime to make a call on the second floor pay phone. We see the items on the floor as George walks past on his way to kill her, but later when he returns and picks up her lipstick everything has been moved. (01:07:25)

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Continuity mistake: When the Canadian motorcycle police drive up and speak to the boat keeper about George Loomis they're all in direct sunlight with no trees anywhere near them. When they leave several shots later it must be an entirely different time of day because shade from the trees across the street covers the entire set. (01:12:25)

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Continuity mistake: After fishing on the Niagara river with the Cutler's, Mr. Kettering pulls his boat up to a dock that is in the shade. In the next shot the dock is in the sunlight. (01:11:30)

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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)

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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)

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Continuity mistake: When the Canadian motorcycle police drive up and speak to the boat keeper about George Loomis, one is wearing a white shirt and the other a blue shirt. In the next close-up shot they're both wearing blue shirts. (01:12:25)

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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)

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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)

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