Nine-year-old Phineas William Walsh has an encyclopedic knowledge of the natural world. He knows that if you wet a dog's food with your saliva and he refuses to eat it then he's top dog, and he knows that dolphins can sleep half a brain at a time. What he doesn't know, though, is why his grandfather died, or why waste-of-flesh Lyle always picks on him. Or why his parents can't live together — after all, when other mate-for-life animals have a fight, it's not like one of them just packs his bags and leaves the country. To make it to-infinity worse, he's worried sick about what humans are doing to the planet, and his mother is worried sick about him. But shouldn't everyone be losing sleep over the fact that a quarter of all Earth's mammals are on the Red List of Threatened Species? So, when a White's tree frog ends up in an aquarium in his fourth-grade classroom, it's the last straw, and he and his best friend, Bird, are spurred to action.