Give Dance a Chance

Effect 

A spectator selects and signs a card from a red-backed deck. The card rises from the pack in full view. Then a second deck, this time blue backed, is introduced and given to another spectator to hold. At the finish, after some byplay, in the red deck, the supposed selection is found reversed—but the signature has vanished. The card is turned over to reveal that it actually belongs to the blue-backed deck.

Attention shifts to the second spectator’s deck. There, reversed in the pack, is the signed selection—the very card that moments ago appeared in the other deck.