Nigel Marven searches the early Mongolia deserts and forests for Therizinosaurus, who has massive and very long claws. Nigel's tent is immediately trampled by a Saurolophus, but he still goes off for his adventure.
On his journey, Nigel dashes across a nesting ground of Protoceratops, and deflects them from attacking him by using a red flag. He enters a forest ruled by Velociraptors, and finds a pack of them bringing down a large male Protoceratops.
In the night, Nigel catches a scorpion and explains that they have been on the planet long before the dinosaurs, and are still alive today. He also finds a group of Mononykus and discovers they have feathers.
The next morning he finds that the Mononykus have eaten his scorpion, and heads out of the denser parts of the forest. There he finds the nesting site of a Therizinosaurus, along with the embryo of one, but also finds herbivore dung around the area. Nigel cannot understand why it is scattered around the nest of Therizinosaurus which he thinks must be a predator.
He continues his journey, and a group of Mononykus run past him, but he finds out that they are actually running away from a Tarbosaurus that is nearby. He narrowly escapes the predator and decides to head to a freshwater lake to see if there are any sings of Therizinosaurus there.
He finds an entire skeleton of one, and reassembles one of the arms. He speculates that Therizinosaurus used the claws for disemboweling prey, but he gets even more confused as he also finds herbivore teeth amongst the bones. Before Nigel can continue searching, he finds a pack of Velociraptors hunting him.
He escapes them by driving them off with a fog horn, and hears some noises by the lake. There, he finds a Tarbosaurus coming down to drink, and while observing it, he finally finds a Therizinosaurus. The two creatures fight each other, with the Tarbosaurus backing down after getting wounded by the huge claws of the Therizinosaurus.
After the Tarbosaurus leaves, Nigel is surprised as he finds a whole herd of Therizinosaurus browsing on the trees, which meant that Therizinosaurus is actually a plant-eater that uses its sickle-claws to drag leaves towards its mouth. Nigel attempts to touch one, and he does. He continues observing it using his camera, and at the end, the Therizinosaurus licks Nigel's camera, which makes him fall.