Charlie Brown and a few of his friends attend a camp, and there they meet Joe Agate, a lying bully who offers to teach kids the game of Marbles without telling them it's for keep. Then he takes their marbles for good. When Rerun is tricked and gets his marbles taken, Charlie Brown must use his own marbles to help get the other kids their marbles back. The only problem is, Charlie Brown doesn't know how to play.