New Ghost Effect?

Here's something I have not seen yet in any scary movie: Ghosts which can only be seen in reflections. Kind of the opposite of Vampires. It requires a very expensive set design due to the complexity required to render accurate reflections.

It may require something like a hallway with a transparent floor, but with reflective surfaces on the sides and ceilings, on both the upright and upside-down renderings of the hallways.

Actors will wander across the transparent floor, being recorded by an upside-down camera, creating the illusion that direct observation of someone in the room is impossible, yet the mind will approximate their position in the room by peripheral reflections. It should create a highly disturbing effect.