Littlefoot is waiting for his father, Bron, who visits the Great Valley with his herd once a year. But a member of Bron’s group, a Nothronychus named Wild Arms, tells him that Bron became stranded at the fire mountain, leaving the rest of the herd to carry on without him. Littlefoot asks for help, but Wild Arms refuses, and the news weighs heavy on him. With worry gnawing at him, Littlefoot decides to set out on his own to search, even as the others soon catch up and join the trek. What begins as a hopeful quest quickly tests their resolve: they manage to keep moving, though they confront the daunting earth divide that blocks their way. Some elders suggest taking the safer Long Valley route, but Littlefoot believes that shortcut would cost valuable time, so he presses on with the group. In a moment of luck and teamwork, they manage to topple a tree and create a crossing, allowing them to push through to the other side.
As night falls, the group endures two close encounters with the fearsome Yutyrannus, and the kids huddle together for safety while the adults realize just how personal this journey has become. The adults decide to pursue them, bringing two younger members along—Chomper and Ruby—to guide the way and offer protection. They entrust Wild Arms, hoping he will lead them back to where Bron was last seen, but his fear of Chomper leaves him overwhelmed, and he collapses, forcing [Chomper] to take the lead by scent and instinct. The following morning brings a rift between Littlefoot and Cera about which direction to take; the disagreement pushes Littlefoot to forge ahead alone again. A swirling sand cloud descends, and Littlefoot ends up trapped inside a hidden cave, where he meets a helpful traveler, Etta, a Pteranodon who seems to know his father and holds clues to Bron’s fate.
Meanwhile, back with the others, [Petrie] has gone missing and ends up encountering a tribe of diggers. The group eventually locates him, and they depart from the diggers, who appoint a new leader for themselves. Inside the cave, [Etta] reveals that Bron’s last rescue mission—his attempt to save Wild Arms—left him stranded in danger. She guides Littlefoot through the darkness, even singing a hopeful tune to help him move forward when hope flickers. The others, pursued by a Carnotaurus, experience a tense pursuit, but Etta skillfully creates an opening by striking a hole in the cave ceiling, enabling the group to escape and reunite with Littlefoot, strengthening their bond.
With renewed courage, the friends head toward the fire mountain and finally locate Bron. He is battered and trapped, yet his resolve remains unbroken. He urges the young ones to retreat to safety, but Littlefoot refuses to leave his father behind. The reunion is tempered by danger, as the group faces additional peril from the Carnotaurus. The chase nearly ends in disaster, until Wild Arms’ fearsome bluster gives way to distraction when Archaeornithomimus appears. Seizing the moment, Etta and the kids spring into action to protect Bron, pouring water onto the flowing fire to slow its advance and using a sturdy tree to pry Bron free. Yet the lava continues to surge, trapping Littlefoot and Bron once more. In a final act of bravery, Bron scoops up Littlefoot and makes a daring leap across the molten lava, a move that finally brings the rest of the herd—led by Chomper—and Ruby to their side.
Reunited, they return home to the Valley, their journey underscoring a central message: true bravery comes from working together and standing by one another. The adventure leaves them with a deeper appreciation for companionship, and a stronger sense of how much they can accomplish when they unite as a team.
