The Killer Prediction

In this convincing trick, the magician shows an envelope and explains that there is a prediction written within. The spectator is given a deck of cards and is asked to mix it and deal cards (face down) onto the table until they feel like stopping. When the letter inside the envelope is read, it states the exact card that the spectator last dealt onto the table.

Materials
A deck of cards, an envelope and a piece of paper.