The hand-held device that controls the mechanical bed has a red button on top and a green button on bottom. But later, when the killer is pressing the controls, the stop and start buttons are in opposite positions.
While watching film clips, Price dressed as Dr. Death is first shown with his mask up and then down and then shown pulling the mask down.
When Paul is first seen in the hospital, he is getting an injection. When the shot switches to over-the-shoulder of the doctor giving said injection, the gray hair on Paul's temples disappears and his mustache gets much darker.
When Julia is dead and Paul seats her at the table, her mouth is open,
but in the next shot of her, it's closed.
In one of the shots when Herbert is revealing his plot, Paul can be seen standing behind the projector, but in the next shot he is leaned on to it.
Julia's dead body is breathing heavily after Paul Toombes discovers her.
When the police are examining the hanged woman's body, the camera shows her face reflected in a piece of gym equipment. Her eyes clearly move as the camera tilts up.
When Paul is searching the house at night, the light of his candle is actually a spotlight, and it is does not keep very good pace with his movements.
When killer is carrying Elizabeth to the boat, there is no wound or blood on her neck or body.
Obvious doll used when Julia is surrounded by flames.
When the fiery climax is shown being recorded, it is via a TV studio video camera. Yet, when the footage is played back, it is on film -- not videotape.