Best horror movie mistakes of 1984
Continuity mistake: When Daniel Stern takes Capt. Bosch down to the sewer area for the first time, the sweat, oil and dirt stains on his tank-top change constantly. This is most noticeable when they first descend into the cellar, where the shirt looks almost perfectly clean after being extremely dirty just a split second before as they start to climb down. Also, a little later, there's all of the sudden an enormous sweat stain on his chest that disappears later.
Plot hole: When Rachael/Ruby is attacked by Pluto in the rafters, Cass, being blind, is able to hear her cry out. When she does, Cass calls out to her by saying "Ruby." However it was a couple scenes later when Rachael tells everyone that she is really Ruby. Cass is surprised to hear this. Therefore, not knowing that Rachael was really Ruby, she should have called out "Rachael" instead of "Ruby" when she was attacked because she didn't know the truth by then.