Step1
The setup for this card trick is crucial. For the purposes of these instructions, the cards used will be the Four of Clubs and Five of Hearts, abbreviated to 4C and 5H, respectively.
The second deck of cards serves to provide a duplicate 4C. On the top of the deck, the top three cards should go: 4C, 5H, 4C. The rest of the deck does not matter. Only the top three will be used.
Step2
Ask the spectator to extend her hand. After she does so, DOUBLE LIFT (term for when a magician lifts two cards but presents it as one) the top two cards. She will be looking at the 5H, but you will actually be holding the 5H and 4C behind it.
Step3
Ask her to name the card she is looking at. When she does so, place both cards back on top of the deck and, while face down, place the top card onto her outstretched hand.
She will think you placed the 5H onto her hand, when the 4C was actually placed.
Step4
Ask her to take her other hand and sandwich the face down card. Ask if she remembers what card she has. She will name the 5H. Tell her to press down as hard as she can so nobody can get into her hands.
Step5
While she sandwiches the card, DOUBLE LIFT the next two. She will be looking at the 4C, but you will have the 4C with the 5H that she thinks is in her hands.
Ask her to name the card she sees. She will name 4C.
Step6
Tell her to watch. You place both cards back on top of the deck and, while face down, remove the top one. She will think it is the 4C when it is really the 5H.
As she watches her hand, rub the 5H over her sandwiched hands. After a bit ask her "Did you feel that?"
Step7
She will respond in a confused manner, but upon turning the card over and revealing it to be the one she thought was in her hand, she will freak.
Have her look at the card in her hands and she will discover it is the 4C. To an average spectator, it will appear that the cards have somehow switched places.