Two men; socialite Henry Fairfield Osborn and fossil hunter Barnum Brown, both want to revive New York's Museum of Natural History. Brown makes a find in Montana that will change the world—the fossilized remains of a Tyrannosaurus Rex. The two men recognize the potential of this discovery to save the museum, and other natural history museums, by making dinosaurs a cultural phenomenon. New York Times best-selling author David K. Randall reveals how an extinct monster changed our understanding of the planet and our own species.