Misbehaving is a magazine story.
At Knapford, Stephen and Bridget hear a loud bang; the trucks are bumping into Thomas. Suddenly, the truck nearest Thomas leans on its side, causing coal to spill. Stephen tells the trucks off and the trucks start feeling bad. The next day, Stephen and Bridget are helping to load mail sacks into Thomas' post train. Unfortunately, the post trolley has a jammed wheel and, after some pushing and pulling by Stephen and Bridget, the mail sacks open and spill the post. Stephen and Bridget learn that even post trolleys are as troublesome as trucks.