The story begins with a sweeping depiction of the North American Cretaceous forest. A massive herd composed of a large number of different species—sauropods, ankylosaurs, hadrosaurs, ceratopsians, ornithomimids and more—are preparing to embark on the annual migration journey. Their trail is stalked by predators, with an early example being a trio of raptors who descend upon the corpse of an old, sick hadrosaur which was unable to embark on the journey. As they head into a forest, a baby Triceratops spies a piece of fruit. Its parent calls out a warning, almost too late, as a tyrannosaur burst from the woods and attacks it. The baby races back towards the heard, narrowly avoiding the jaws of the tyrannosaur, as the parent rushes to the rescue, crashing into the carnivore. The baby makes it to the safety of the herd, which closes ranks in the face of the marauding predator. Rather than trying to find a gap in the herd, or risk an attack on a healthy adult Triceratops, the tyrannosaur decides to withdraw and wait for a better opportunity.