Revealing mistake: The "Old man-ghoul" changes appearances drastically throughout the entire movie. In some scenes, it is Bela Lugosi in vampire cape, in others it is the famous "double" who is a head taller than Lugosi, a lot thinner and has a different hairstyle. He covers his face with his cape, but this does not help a lot...
Continuity mistake: At the beginning of the movie the narrator states that the funeral for the old lady is taking place at dusk. The next scene, in the airplane, is supposed to be taking place at the same time yet when the co-pilot calls the control tower he says that it is fifteen minutes to four and he doubts that the controller would be awake at this time of the morning.