Revealing mistake: When the housekeeper hangs herself, you can tell the rope isn`t even around her neck. It is obviously connected to a harness around her torso.
Revealing mistake: When Lewis is trying to get Gage off him, as he's struggling with the scalpel, you can plainly see its not really Gage but a dummy made to look like him. Looks like a doll.
Revealing mistake: When Lewis gets out of the tub and has a towel around him, you can see he has underwear on.
Revealing mistake: When Louis goes to give Gage the shot if you look closely you can see that the needle doesn't leave a puncture mark.