The nursery girl is a variation on an optical illusion known as a Pepper's Ghost. The image is formed by viewing a reflection in a pane of glass. The actual image is a projection on a screen that is not in the direct view of the audience. Careful placement and lighting of the various elements in the room cause the appearance of a moving, transparent figure. A very high contrast filmed scene (white against black) is necessary for the illusion to work well.
The pictures on this page were taken during various filming sessions for the effect. The scene was refilmed several times due to concept changes and the durability limitations of Super-8 film.

Mary Beth is also the voice of the Talking Statue and the Crypt Ghost.

