After Charlie Brown wakes up one morning, he is shocked to see the sun resembling a baseball! He tries to forget this, but anything round (the moon, a scoop of ice cream, etc), keeps resembling a baseball. When Linus notices a rash on the back of Charlie Brown's head that resembles a baseball's stitching, he recommends Charlie see his pediatrician.
The pediatrician recommends Charlie go away for awhile, and Charlie decides to go to camp. So noone sees the rash on his head, he wears a paper sack over his head. At camp, the other kids decide to elect a Camp President, and one half-jokingly suggests "nominating the kid with the sack on his head."
Surprisingly, Charlie wins the election. A number of kids soon take a liking to him, and he becomes quite popular. After some time, Charlie decides to take the bag off his head, and goes out to watch the sun rise. However, his fear of seeing a baseball is turned to shock, when the sun resembles Alfred E Neumann's head from MAD Magazine.
Charlie Brown attempts to fly a few kites, but the Kite-Eating Tree devours them. Fed up with this, Charlie threatens to bite the tree if it doesn't let go of his latest kite. When it refuses, he makes good on his threat, leaving bite-marks in the trunk.
Shortly afterwards, the Environmental Protection Agency sends Charlie a letter, and he decides to run away to avoid being detained by the EPA. Eventually, Charlie finds himself in a new suburban neighborhood, and befriends a group of younger kids. As they are part of a baseball team, they ask Charlie to be their manager. Eventually, the kids plan to play their first game...only to find that Charlie Brown's former team is challenging them! Linus tells Charlie that he is also safe to return home, as the Kite-Eating Tree blew down during a big storm, and the EPA has called off their search.