The film, narrated by Stephen Fry (UK) and Simon Kerr (US), opens on a sunny summer day in Northern Alaska, about 70 million years ago, where a thriving herd of Edmontosaurus and a heavily armored Edmontonia feed among lush Arctic vegetation. Scar, a young Edmontosaurus, enjoys life with his extended family, while a curious encounter with a young Alaskan Troodon named Patch hints at a changing balance of life in this frozen world. Patch has spent the summer hunting baby Edmontosaurus, but as the youngsters grow, even his nimble predation becomes harder. A chase after an Alphadon shows Patch’s hunger, yet another Troodon seizes the fleeing mammal, and Patch’s impatience grows.
As night falls for the first time, winter’s approach tightens its grip. Scar narrowly dodges a lethal strike when a dark shape reveals itself—a Gorgosaurus that rips into his world with a single, devastating blow to his face. The threat season thickens when a herd of Pachyrhinosaurus arrives, competing for the dwindling food and pressing the herd’s survival. Scar glimpses his old friend the Edmontonia, who now leans on the rotting wood of a fallen tree and the insect larvae that cling to it, feasting with mixed success. With the sun sinking, the Pachyrhinosaurus herd moves on, and the Edmontonia remains behind, storing fat for the lean months to come.
Meanwhile, Patch and the Troodontids are scavenging on the carcass of a fallen Edmontosaurus, while the Gorgosaurus resurges. The tyrannosaur’s encounter with the Troodons ends in a wounded defeat for the predator, and Patch’s hunger grows more stubborn as he must hunt harder for prey. Far to the south, the Edmontosaurus and Pachyrhinosaurus herds press onward toward warmth, while the heavy-edged Edmontonia lingers behind, protected by armor and patience.
The long march continues as winter tightens its grip. The herd pushes south toward Alberta, compelled by cold and scarcity, but the Edmontonia remains behind, having stored fat to weather the cold. Patch, now more determined, and the Troodons feed on the dead Edmontosaurus as the Gorgosaurus stalks the edge of the scene, wounded from a prior clash. The hunter’s struggle intensifies, and Patch’s resolve is tested as he seeks new ways to catch prey.
A massive blizzard looms, and Scar collapses in the storm. An older male Edmontosaurus arrives to help him push forward through the whiteout, their strides synchronized as they endure the brutal weather. Unseen danger awaits as the herd unknowingly steps onto a frozen sea inlet; the ground fractures beneath them, and some are dragged under by a pack of mosasaurs known as Prognathodon. Scar, unable to swim at first, is forced into the icy water and begins to swim toward the shore, fighting for survival.
Back in Alaska, Patch tries to impress a potential mate with a display, only to be outshined by a more experienced rival. The Edmontonia, meanwhile, finds only a last leaf to sustain her as the cold intensifies. A cruel turn of fate comes when an injured female Pachyrhinosaurus calls out, and Scar’s old companion is left to face the elements alone. The Albertosaurus, having survived earlier battles, begins to stalk anew, and the older ally’s death becomes a sobering reminder of the harsh law of predators and scavengers in this world.
Six hundred miles farther south, the Edmontosaurus herd threads through a field of volcanic ash. Scar notices a dark shadow—a flock of Quetzalcoatlus—circling to feed on the dying and the weak. While the feathered scavengers wheel, a group of Albertosaurus roams nearby, waiting for the herd to come within reach. The predators launch a coordinated ambush as volcanic activity erupts in the distance, triggering a cascade of rock, mud, and water that sends the landscape into chaos. Scar flees up a wintry slope as the Albertosaurus, injured in the eruption, is swept away by the mud and loses its pursuing edge.
Back in the Arctic, Patch continues his courtship dance but loses to a seasoned rival, while the Edmontonia has found a last, fragile leaf to sustain her. A split moment later, the log she stands on cracks and she slides helplessly down the snowy slope, vulnerable to the elements. The story cuts to Scar, who calls out to his family across the distance, but the calls that reach him are those of those who did not survive the journey—the old bull Edmontosaurus and an injured Pachyrhinosaurus already gone.
The Albertosaurus, having endured, resumes its pursuit. Scar’s hunt for safety leads him along a chase that ends with a clash of old strength and new risk. The predator’s pursuit continues until the two fall from a cliff in a desperate embrace, leaving Scar alone once more to face the world.
In the north, Patch adapts by listening for Alphadons beneath the snow and becomes a resourceful hunter in the cold. He and several fellow Troodons strike at an overturned Edmontonia, but the Gorgosaurus, fully healed, arrives to interrupt the attack and drag the herbivore away. The Edmontonia fights back with powerful shoulder spikes, forcing the predator to retreat to its lair, nursing a broken leg. As dawn breaks, Scar grows weaker, and a lone Quetzalcoatlus follows the vulnerable herd, sensing the change in his strength. The injured Pachyrhinosaurus returns, and the ceratopsian herd begins to cross a river under guard from the rising sun.
Then the sea of danger rises again as Prognathodon mosasaurs descend, dragging many beneath the icy waters. Scar dives into the peril, fighting the current and the hungry predators while the rest of the herd makes its precarious crossing. He finally reaches the far bank, where he reunites with the Edmontosaurus herd and finds safety among familiar faces. As spring’s warmth slowly returns to the Arctic Circle, Edmontonia feeds again on tender greens, and Patch, having endured the trials, finds a mate by offering scavenged meat from a fallen Gorgosaurus. The cycle of life resumes, and the Edmontosaurus herd prepares to head north once more when summer returns, continuing their ancient, shared journey through a world of peril and renewal.
