This is an amazing transposition between a playing card in the magician’s hand, and one in the spectator’s pocket!
A packet of four cards is shown which consists of three identical (duplicate) cards and one different or odd card. The odd card along with one of the duplicate cards are placed into a spectator’s shirt pocket.
Now the odd card is removed from the shirt pocket and placed with the other two duplicate cards being held by the performer. The odd card is turned over so its back is seen. Then with a snap of the magician’s finger the odd card is turned over to show that its face has changed to match the other duplicate cards, leaving a packet of three identical cards in the magician’s hand!
The spectator removes the card from their pocket to find that the duplicate card that was there has changed into the odd card that was in the magician’s hand!