To effective celebrate Earth Day for Ms. Frizzle, the kids decide to rent a cocoa tree from the Brazilian rain forest. Ms. Frizzle is excited from the gift, and the kids travel to the rain forest immediately. However, they are disappointed when they arrive there, as the cocoa tree has no cocoa beans. Something in the ecosystem has gone wrong, and the Inspector who acts as a ranger is suspicious.
The kids learn that the cocoa beans are made from pollen from certain insects, but the trees are too malnourished to attract the insects. By more observation, the kids learn that the trees can't get enough nutrients from the ground because it doesn't seem like a marsh. The peccaries, native pig beasts, are the ones who sift the mud around and spread nutrients for each trees to absorb. There is no mud, as someone deliberately placed astroturf all over the forest floor. Inspector 47 soon admits to it, and the authorities seize him.