Double Crossed is one of the most powerful "In the hand" card effects you will ever perform!
Your spectator counts off twenty cards from a shuffled deck, then the cards are separated into two groups of ten. One packet is given to your spectator to securely hold (placing them between their hands or in their pocket). The remaining ten cards are openly spread, you then ask your spectator to SIMPLY THINK of two different cards.
You tell your audience you will cause the two thought-of cards to vanish from YOUR packet, fly through the air invisibly, and arrive in THEIR packet!
The spectator counts the cards in your packet and is amazed to find that only eight cards remain! The eight cards are shown one at a time, on both sides, proving that the mentally selected cards have vanished! Your spectator counts the cards one at a time only to find there are now TWELVE CARDS!
You ask: "For the first time, what are your thought of cards?" Your spectator names them and finds they are now missing from your packet and have magically appeared in their packet!!!!