A paleontologist named Zack embarks on an exciting fossil hunting adventure in Alaska with his nephew Ricky and niece Jade while their parents enjoy a vacation in Europe. During their expedition, Ricky encounters a mystical, anthropomorphic raven named Alex, who magically transforms into his prehistoric ancestor, the Alexornis. Alex shares an incredible tale set in the Late Cretaceous period, approximately 70 million years ago, about his dear friend Patchi.
Patchi, a small and frail member of a group of Pachyrhinosaurus hatchlings, often finds himself the target of bullying by his older brother Scowler. Their father, Bulldust, is the revered leader of their herd. As Patchi's mentor, protector, and teacher, Alex strives to help him win the affections of Juniper, a female Pachyrhinosaurus, though she migrates south without him. During a perilous encounter, Patchi is attacked by a Troodon but is saved by his father, leaving him with a distinctive hole in his frill. Alex reassures Patchi that he is "destined for greatness" despite his challenges.
As Bulldust leads the herd southward, they face a devastating storm and a forest fire that forces them to flee. In this chaos, a menacing pack of Gorgosaurus launches an attack, resulting in the tragic loss of Patchi and Scowler's family. In a brave attempt to defend them, Bulldust fights off their alpha, Gorgon, but ultimately falls victim to the ferocious beast. In the aftermath, the surviving members of Patchi's herd merge with Juniper's group under the leadership of Major.
Later, Patchi, Scowler, and Juniper are swept away to the ocean, with Alex faithfully following. As they reach a beach, Scowler, selfishly seeking food, abandons Patchi and Juniper. Nevertheless, the duo perseveres, navigating their way back to find their herd alongside Scowler.
Time passes, and Scowler, having matured into the new leader of the herd, chooses Juniper as his mate, leaving Patchi heartbroken. Taking a daring approach, Scowler recklessly leads the herd onto a frozen lake, but Patchi manages to guide most of them to safety. However, consumed by jealousy and fearing that Patchi plans to usurp him, Scowler challenges his brother to a duel for leadership. Due to his size and strength, Scowler quickly gains the advantage, trapping Patchi beneath a tree and expelling him from the herd along with Juniper.
Devastated and feeling hopeless, Patchi contemplates surrendering to scavengers, but Alex inspires him to fight for a cause worth dying for, just as Bulldust had done. Fueled by newfound resolve, Patchi breaks free and swiftly catches up to the herd, only to be confronted by Gorgon and his pack once again. Despite being overpowered, a remorseful Scowler urges Patchi to escape and lead the herd to safety. Defying expectations, Patchi rallies the herd to confront Gorgon and his pack, ultimately achieving victory and avenging their father's death by defeating Gorgon.
In a powerful moment of reconciliation, Scowler acknowledges Patchi's leadership, passing on the torch as Patchi and Juniper find love and start a family, with Alex proudly taking on the role of the uncle. Back in the present, deeply moved by Alex's story, Ricky presents Gorgon's fossilized tooth to Zack and Jade, who had previously unearthed Gorgon's ancient skeleton nearby.
