Jacob and Buford build the 'Predicto-Magic Machine' for a fortune-telling booth at the school fun fair and are amazed that it really does predict the future. Fun turns to mayhem when Principal Greedyguts grows more and more desperate to know why the school superintendent wants to talk with him. The future that is revealed causes Greedyguts to celebrate, and the kids to realize that while they can't change the past, they must try to affect the future.