Long before ice sheets buried it, Antarctica was a subtropical world of dense forests and river deltas. This film follows a team of palaeontologists into the Transantarctic Mountains, digging through frozen rock for fossils that reveal what lived there before the freeze. Among the finds is Lystrosaurus, a stubby-legged reptile that survived Earth's worst mass extinction and turns up on nearly every continent that once fit together as Pangea. The film also traces Cryolophosaurus, an apex predator that ruled the ancient landscape, and looks at how forests managed to grow through four months of total polar darkness each year. Fieldwork scenes show the team hauling equipment across exposed rock faces and cutting fossils free from stone that has held them for hundreds of millions of years, while the narration walks through what each specimen adds to the picture of a continent that used to be unrecognizable. The result connects present-day Antarctica to a version of itself that had rivers, canopies, and predators instead of ice.