Dinosaurs spend the early Jurassic as a modest assortment of small creatures and emerge by the late Jurassic as the dominant carnivores and giant herbivores that ruled the planet for millions of years. What happened in between, during the middle Jurassic, has been one of paleontology's most stubborn gaps, with too few fossils to say whether mass extinction, environmental upheaval, or something else drove the transformation. The film follows paleontologist Oliver Rauhut to a site in the Argentine wilderness where his team, working across thousands of square miles of mid-Jurassic rock since the 1990s, uncovers two giant meat-eating dinosaurs, six long-necked giants, and a wider ecosystem of early mammals, crocodiles, fish, and plants preserved together. Rauhut calls the site an extraordinary window on the period; geologist Phil Manning compares the find to a holy grail of dinosaur paleontology. The footage follows the excavation itself, fossil by fossil, as researchers piece together what the missing middle chapter of dinosaur evolution actually looked like.