Show a large envelope with a prediction inside.
A spectator selects a card. Let's say the nine of hearts.
Proclaim that your prediction is correct! Open the envelope and remove a framed piece of transparent plastic, showing the entire deck of cards, faces on one side and backs on the other!
Of course, the prediction is correct - all the cards are there! Not very impressive.
Offer to take it a step further. Ask the spectator to hold her hand above the frame and concentrate on her card.
When she removes her hand, one of the face-up cards has turned face-down!
Turn the frame over, one card is face-up! It is their selected card!
And, you can hand the board out for immediate examination. They will find nothing!
Self contained. Mechanical. Nothing added or taken away. The gimmick is so clever.