The Effect
A spectator is asked to shuffle the cards, then remove any 12 cards from the pack and to further shuffle these 12. Whilst this is being done the magician writes a prediction on a piece of paper which he places face down on the table. 

The spectator now takes any 4 cards from his selected 12 cards and lays them in a row face up on the table. The remaining 8 cards are put with the rest of the pack. This is now taken up, and from it cards are dealt onto each of the face-up cards so as to bring its value to 10. For instance, if it’s a 4, then 6 cards are to be dealt on top of it. All picture cards, however, are valued at 10 so no cards are put on these.

This having been done, the total value of the 4 cards is ascertained. For example, supposing the 4 face-up cards happen to be the 3 of Hearts, the 7 of Clubs the Jack of Spades and the 4 of Diamonds, their total value would be 24. The card which lies at that number is now counted down to in the pack that remains. When it is turned over, amazingly matches the original prediction.