Maxello Magic

The magician takes out two cases that have been pushed together. He draws a red-backed card from the red case, which he then presents to the audience. A member of the audience chooses a card from the deck and notes it. The magician replaces the deck in its case, then opens the blue case and takes a blue-backed deck out of it!

Among the blue cards is a red card, which is none other than the card chosen by the member of the audience!