Enredo

Tragedy forces a caveman and a dinosaur to rely upon each other for their survival.

Spear, a primitive man, spear-fishes in a rainforest stream, gathering his catches on the end of a rope. Suddenly, a huge crocodilian bursts from the water and tries to grab Spear, but he dives underwater and hides behind a rock until the crocodilian swims away. Spear picks up his fish and heads away from the stream.

As he walks back through the rainforest, a large pterosaur lands nearby and smells his fish. Spear hides in a hollow tree trunk and waits with baited breath as the pterosaur probes its beak inside the tree, following the scent of the fish. Eventually, the creature hears a call from far away, and flies off after it. Spear emerges and continues his journey. Passing through a hilltop clearing, he sees a plume of smoke rising from his campsite and smiles with relief.

Walking across a plain as he nears his home, Spear spots a large tyrannosaurid footprint before hearing a woman's scream. He drops his fish and sprints for his camp, terrified for the safety of his family. He arrives just in time to witness two tyrannosaurids eat his mate and his two young children. Overcome by grief and rage, he throws his spear into the snout of one of the tyrannosaurids, drawing their attention. He dodges their attacks and jumps to retrieve his spear, landing and standing his ground against the beasts. They prepare to attack him before hearing a call from a much larger tyrannosaurid, presumably their mother, and leaving to go and follow her. Spear is left alone, devastated.

During the night, Spear climbs a high cliff face and stands on the edge, preparing to take his own life. He steps towards the edge but ultimately does not jump, sitting sorrowfully until the morning. As he watches the sunrise, he sees a vision in the sky of his mate and children looking down at him, and smiles as his desire to survive returns.

In the daytime, Spear returns to his fishing spot. While eating, he spots the shape of a tyrannosaurid hunting in the foliage. Bent on revenge, he picks up his spear and begins tracking the animal. He follows it into a large cave, where he realizes that it is not one of the dinosaurs that ate his family, but a mother tyrannosaurid, Fang, bringing food to her two babies. Confused and enraged, he stands his ground as Fang watches him defensively. Suddenly, the two tyrannosaurids that ate his family enter the cave behind Spear. He dodges, and recognizes them as they advance on Fang and her babies. Realising she is going to lose her family to the same predators that took his, Spear throws his spear into the snout of one of the tyrannosaurids and runs towards it. Fang notices this and turns her attention to the other predator.

Viciously defending her young, she bites the open mouth of the tyrannosaurid and rips its snout off, leaving it to fall and bleed to death. Running towards the other predator, Spear grabs a rock and breaks its leg before climbing onto its head, ripping out one of its teeth, and stabbing it repeatedly with the tooth. As the creature reels, he jumps off it, retrieves his spear, and throws it through the tyrannosaurid's neck, killing it. His family avenged, Spear's rage dissipates and he collapses onto his knees.

Fang's babies approach Spear and nuzzle him in gratitude for saving them. Spear is cautious at first, but when he sees that Fang also understands that he helped them, he embraces the babies and enjoys a moment of happiness.

Suddenly, the gigantic mother tyrannosaurid from before bursts into the cave and goes after Fang and the babies. Fang tries to stand in its way, but a single tail swipe from the huge beast sends her flying. To her and Spear's horror, the mother tyrannosaurid corners the babies and eats them both. Spear and Fang fruitlessly try to injure the giant before eventually working together, with Spear riding on Fang's back up the spine of the tyrannosaurid before plunging his spear into the back of its neck, killing it. Dismounting its head, Spear sadly looks over at Fang who is forlornly sniffing the nest where her babies were, before leaving the cave.

Spear walks along a beach and realizes that Fang is following close behind him. She slowly approaches him, provoking caution from Spear, but she simply looks at him sadly and lies down on the sand. They both seem aware that they have shared a common tragedy. Spear pitifully looks at Fang before smiling as he realizes that they can work together to survive.