While cleaning out the basement, Tobi and Marina discover an old video recording: In it, eight-year-old Tobi hosts a show he invented himself about the earth in our soil—and asks his very first “Checker question”: Who leaves the most powerful traces in the soil?

But Tobi has forgotten the answer. He sets out on a search for clues, embarking on his greatest adventure yet. This takes him to the flora and fauna of Madagascar, the permafrost region of Spitsbergen, and the traces of the ancient Maya in Mexico. Only when he realizes what connects all soils and what that has to do with us can he answer his greatest challenger: himself.