David tells about the childhood of gnomes, using his friend Harry and his family as an example. David tells about Harry's children, Billy and Belle, and the way children grow up. It is also Billy and Belle's birthday, and David takes Susan to the party. On the way, he helps a mother hen learn how to keep up with her chicks. Then they go to the party. While Susan plays party games with the other children, Harry takes David to the forest nearby and tells how he is sad because the men from the city are cutting down all the trees. When they go back to the party, they learn that the trolls have shown up. The trolls throw apples and sticks at the gnomes, and they all run into Harry's house. David and Susan go back out and try to think of a way to get even with the trolls. They see the trolls asleep in a tree, and then a bulldozer from the city comes by. Some men take a chainsaw and cut down the tree, sending the trolls crashing to the ground.
