Cut the deck and have the spectator return his card, the ace of spades, to the top part of the deck. Complete the cut and place the bottom card, the nine of spades, on top of the spectator’s card.
This image shows an exposed view as if you were looking-up from underneath the cards. As you can see, the nine of spades will soon go on top of the ace of spades. At this point, you still do not know the spectator’s card is the ace of spades.
