Mary, Laura, and Mr. Edwards' adopted son, Carl, go along with Charles and Mr. Edwards to a train station. The three children wander into the caboose. The caboose then begins to move backwards, going faster and faster. Another train is coming the opposite direction...

Mr. Edwards and the residents of Walnut Grove make friends with an orangutan. But the friendship and the fun-loving primate's life may be short-lived when Nancy and Mrs. Olesen cause trouble.