Errol Morris interweaves the stories of four men, each driven to create eccentric worlds from their unique obsessions, all of which involve animals: a lion tamer shares his theories on the mental processes of wild animals; a topiary gardener devotes a lifetime to shaping bears and giraffes out of hedges and trees; a man fascinated with hairless mole rats; and an MIT scientist who has designed complex, autonomous robots that can crawl like bugs.