A self-contained mental MIRACLE with BAFFLING results!
You shuffle a deck of cards and 4 cards are freely selected, either by one person, or 4 different people. They each give their card a number from 1 - 10.
Further cards are added to their card to make the total up to 10. So, if they selected 2, then you add 8 cards. If they selected 6, you add 4 cards, etc.
You then add up the total of the 4 numbers at the beginning and deal down to that card, say the 16th card.
You proceed to open the envelope that has been on display the WHOLE time and it has the Six of Hearts in it. You turn over the 16th card on the table and it MATCHES!
For the final KICKER, you turn over your prediction card and it is BLANK. When you now spread the entire deck, it is also completely BLANK!