The movie begins with helicopter pilot and guide Don Stober flying guests high above the lush landscapes of a vast National Park. He explains that the forest remains a pristine reflection of its ancient past, untouched since the times of the Native Americans.
As the story unfolds, two female hikers are in the midst of breaking down their camp when tragedy strikes: one is viciously attacked and killed by a bear. The surviving hiker finds refuge in a nearby cabin, but her safety is short-lived when the bear breaching the walls to get to her. Meanwhile, the Park's Chief Ranger, Michael Kelly, along with photographer Allison Corwin, who is also the daughter of the park's restaurant owner, lead a search for the two women. Their grim discovery of the first woman’s disfigured remains inside the cabin leaves them reeling.
In a hospital, a doctor confirms to Kelly that both women were fatalities of a bear attack. Charley Kittridge, the Park Supervisor, swiftly places blame on Kelly, insisting that he and Naturalist Arthur Scott failed to relocate bears from the park ahead of the tourist season. A heated exchange erupts between them regarding the park's closure; ultimately, they opt to move all hikers away from the mountains while permitting campers to stay in the lower regions. When confronted, Scott reassures them that all bears are accounted for, implying that the predator in question is not native to the area.
However, danger escalates when a female ranger meets a brutal end during a swim near a waterfall, prompting Kelly to enlist Stober's help for aerial searches. High above the treetops, they spot a figure in the woods, only to uncover that it’s Scott, donning an animal skin in a desperate attempt to track the enormous bear. He warns them that they are dealing with a prehistoric grizzly bear that stands at least 15 feet tall. Skeptical at first, Kelly and Stober cannot dismiss the mounting evidence as further chaos ensues at a crowded campground where the vicious bear attacks and kills yet another woman.
As national media coverage escalates, Kittridge’s refusal to close the park initiates a troubling decision allowing amateur hunters into the wilderness. Kelly, Stober, and Scott express their disgust at this turn of events. Later, a lone hunter narrowly escapes an encounter with the bear, while a ranger stationed in a lookout tower falls victim to the creature's relentless fury when it demolishes the structure.
With anger boiling between Kelly and Kittridge over the ongoing dangers, Scott makes the decision to track the bear alone. On the park's edge, chaos erupts once more as a mother and her child are attacked; the mother perishes while the child endures horrifying injuries. This shocking event finally compels Kittridge to relent and allow Kelly to close the park along with a ban on hunting.
In a bid to capture the elusive bear, Stober and Kelly set a trap using a deer carcass. They chase after the beast only to realize they have been led into a trap themselves. Meanwhile, Scott uses his own strategy, dragging the carcass on horseback to lure the beast, but he unexpectedly faces the bear, which mauls his horse and leaves him unconscious. When Scott comes to, he finds himself partially buried, but the grizzly soon returns to finish the job.
The devastation deepens as Kelly and Stober discover Scott's lifeless body. Driven by sorrow and determination, they return to the helicopter to search for the bear from the sky. Spotting it in a clearing, they land quickly, but the bear attacks their helicopter, throwing Stober away from the craft. In a desperate act of survival, Kelly retrieves a bazooka from the chopper and, just as the bear closes in, fires it at the creature, annihilating it instantly.
As the remnants of the grizzly burn, Kelly is left standing in a moment of quiet reflection, staring somberly at the loss of both the bear and his companion, Stober, who lies lifeless nearby.
