Félix, at nine years old, has an encyclopedic knowledge of the animal kingdom and nature, and he is deeply concerned about the fate of the planet. Both at school and at home, his questions, logic, and arguments challenge the established order, often confusing or exasperating the adults around him.

One day, his teacher introduces a new "class pet": a White's tree frog from Australia, trapped in an aquarium. This is the last straw! Félix and his best friend Oli have no choice—they must take action!