The Hidden Hand by Sudo Nimh

The Hidden Hand is a brand-new idea that uses an old method in a completely unique way for secretly gaining access to hidden information quickly, easily, and without detection. With it, a wide range of possibilities exist. For example, imagine this:

Three spectators are each given a business or index card to make a drawing of anything they wish. They mix them up and leave them face down on the table or hide them inside a box which they lock. Without EVER touching their drawings or handling the box, you pick up a pad and can immediately begin duplicating each spectator’s drawings!