Beaver Ben is a hardworking beaver who is building a dam when he realizes his favorite tool is missing. Harriet the Hen plays a series of pranks on him, leading to a frustrating and challenging day for Beaver Ben. However, Harriet reveals that it is April Fools' Day, and she was playing jokes on him all day. Beaver Ben forgives her but decides to get revenge. They both learn the importance of knowing when to be serious and when to have fun, and the power of humor in difficult situations.