Terry and his friends work as a logging team. Each machine has a special job to do. However, some of the machines become careless and cut down trees too close to the river. A thunderstorm then causes erosion and the river is filled with mud.

The fish in the river will be killed unless the machines quickly repair the damage they have done to the ecology.

Terry and the others learn that teamwork and attention to the work plan is necessary to get the job done. They also learn how important it is to protect the ecology.