Decorate a wall with a large oval mirror frame and a pane of glass instead of a mirror. Coat the glass with a sheet of aluminized window reflector (available at hardware stores), making the glass into a 2-way mirror. Put an operator behind the glass in a darkened compartment, with a dim green bulb in his compartment and a bright light in the viewer’s side, connected by dimmer switches. The viewer will look into the mirror and see only his own reflection when the light is on his side. The operator (dresses in black except for a white face) should dim down the viewer’s light and turn up the green light on his face. The viewer will them see the face in the magic mirror talking to him.