The Ulam, a tribe of primitive cavemen, fiercely protect their precious flame, which they rely upon to ignite larger fires. Their lives spiral into chaos when they are driven from their home following a brutal clash with the ape-like Wagabu. In a desperate bid for safety within a marsh, the unthinkable happens—their fire is extinguished. Faced with this dire situation, the wise elder of the tribe decides to send three brave men—Naoh (Ron Perlman), Amoukar (Brian Gill), and Gaw (Everett McGill)—on a daunting quest to reclaim the vital element of fire.
As the trio embarks on their perilous adventure, they confront various threats, including the menacing Kzamm, a tribe of more primitive, cannibalistic beings who hold the fire they desperately seek. The cunning plan is to snatch this precious resource right from under their noses. While Gaw and Amoukar lure the Kzamm away, Naoh engages in a fierce battle with the remaining warriors. However, the price of victory is steep—Naoh suffers a painful injury that leaves him in distress. Despite the odds, they successfully seize fire from the Kzamm’s camp and prepare to make their way home.
Their journey takes a surprising turn when they encounter Ika, a young woman held captive by the Kzamm, who decides to join them. Ika demonstrates her resourcefulness by creating a makeshift poultice to tend to Naoh's wounds. Tensions escalate when Amoukar makes an aggressive advance towards Ika, only for her to seek refuge with Naoh, leading to a troubling assertion of dominance as Naoh forces himself on her, altering their dynamic forever.
As fate would have it, Ika realizes they are near her homeland and tries to convince her companions to join her. When they decline, they part ways, but soon Naoh is compelled to turn back, with Gaw and Amoukar reluctantly following. They ultimately reunite, but danger lurks ahead. Naoh’s curiosity leads him into a trap—quicksand, where he nearly meets his demise. He is rescued but subsequently captured by Ivaka, Ika's own tribe. Here, Naoh faces humiliation and is subjected to mating with the tribe's larger women, whilst Ika is ostracized and unable to be near him. The Ivaka then reveal their advanced fire-making techniques to Naoh, further complicating his situation.
In a twist of events, Gaw and Amoukar track down Naoh among the Ivaka but find him hesitant to leave the fiery safety he'd stumbled upon. Under the cover of night, Ika helps orchestrate an escape by knocking Naoh unconscious. As they journey back home, Naoh attempts to rekindle his relationship with Ika, learning from her how to be more intimate in their encounters.
Just as they near the marsh that started this wild adventure, they are ambushed by rival Ulam, eager to claim the fire for themselves. Utilizing the advanced weaponry they acquired from the Ivakan, Naoh and his friends successfully fend off this challenge.
Upon their triumphant return to the Ulam, they present the coveted fire, bringing joy to their people. Yet, a mishap during the celebration leads to the unthinkable— the fire is extinguished once more. Determined to reclaim their flame, Naoh strives to remember the techniques learned from the Ivaka, but struggles until Ika steps in, finally igniting hope once again, much to the tribe’s elation.
Months pass as Naoh and Ika look forward to the future—ready to embrace the joys of parenthood together, marking the culmination of their arduous journey.
