The film is a tracking shot into the theatre where the film is being projected. The theatre is in darkness, as it would be during a projection, but there is no audience. The projector is running without film in it, so on the screen is a rectangle of light. The shot centres this white rectangle, then slowly zooms within it. The print runs out of the projector, leaving as a reality a rectangle of light on the screen, which only a moment before the audience had seen as an image.