Dr. Jane Tiptree, Diane Ladd, a reclusive scientist, has withdrawn from public life to conduct sequestered research for the Eunice Corporation. DARPA watches warily as she pursues genetic work with chickens, though they lack legal grounds to interfere with her experiments. While in transit, one of Tiptree's chickens hatches a reptilian creature, which kills the driver and escapes into the surrounding countryside. Meanwhile, in the small town of Climax, Nevada near her lab, residents begin suffering from a mysterious illness with flu-like symptoms that disrupts daily life.
At a nearby quarry, watchman Doc Smith, Raphael Sbarge, guards excavation equipment from concerned environmentalists. He reports a trespasser, Ann 'Thrush' Jennifer Runyon, and Sheriff Fowler, Harrison Page, investigates a string of gruesome killings that seem linked to Tiptree's missing creature, a Deinonychus. Among the victims is the daughter of Eunice employee Jesse Paloma Frank Novak, a tragedy that pressures the town to search for answers. Before Paloma can mount a protest, Tiptree lures him into a laser-protected dinosaur pen where a fully grown Tyrannosaurus rex kills him in a brutal display.
Despite the mounting deaths, Thrush and a group of activists handcuff themselves to excavation equipment in a quiet form of protest. They are attacked by the Deinonychus, and everyone except Thrush is slaughtered. Grieving and shaken, Thrush is brought back by Doc to his trailer, where she survives another onslaught by the creature. Doc then discovers a truck carrying two Eunice corpses and uses a radio to contact Tiptree, deducing that the monstrous animal originated from her facility. As he moves toward the lab, Fowler discovers a dinosaur embryo hidden in a carton of eggs and takes it for further investigation.
Doc infiltrates Tiptree's laboratory and, at gunpoint, confronts her as she reveals her grim experiment subjects to him. The town's mysterious illness is revealed to be caused by infected chicken eggs, which release a lethal airborne virus that impregnates women with dinosaur embryos. Her objective is almost mythic in scope: exterminate humanity to allow dinosaurs to reclaim the Earth. News of the town's deaths reaches Eunice sponsors, who in turn trace the outbreak back to Tiptree, prompting the government to place Climax under quarantine and to consider drastic measures against civilians.
With the illness spreading quickly, Fowler responds to a disturbance at a pet shop and faces a Deinonychus in a deadly encounter; both he and the dinosaur suffer fatal wounds. In a secure underground bunker, top government officials begin plotting the repopulation of humanity in response to the virus, envisioning a harsh new order built on strict fertilization controls and artificial wombs. Back at the laboratory, Doc attempts to escape with a cure, but his path collides with the dangerous creatures as he mistakenly enters the dinosaur pen. Tiptree releases the T. rex, which relentlessly pursues Doc out of the facility. In a shocking turn, Tiptree, already infected, births a dinosaur before she dies from the illness.
Doc returns to Thrush, who has been exposed to the illness. The T. rex roams the quarry, and Doc uses a skid-steer loader to combat the monstrous predator, eventually disemboweling and killing the creature with Thrush's aid. He injects Thrush with the experimental serum, but government soldiers, alerted to his presence, shoot him down and burn both his and Thrush’s bodies. In the blaze, the life-saving serum is destroyed, leaving the town to face the consequences of a world forever changed by the dinosaur threat.
