Ruben Castle [Robert Urich], a brutish and alcoholic New York City police officer, quits his job and becomes sober, allowing him to reunite with his estranged teenage daughter, Mackenzie [Marin Kanter]. Ruben decides to bring Mackenzie with him to Colorado, where he plans to start a new life.
En route, the pair are stranded near the rural small town of Buffalo after their trailer suffers a tire blowout. Mackenzie rushes to find a tow truck, and crashes into the vehicle of the newly appointed town sheriff, Harriet Purdue [JoBeth Williams]. Ruben and Mackenzie park their trailer in a campground and begin to get acquainted with the locals.
Ruben encounters Harriet and learns she is investigating a series of mysterious cattle mutilations, which have spurred conspiracy theories about UFOs and a Satanic cult in the area. The two officers, each hardened by their careers, strike up a wary but growing friendship as they share stories from the beat and compare notes on the strange happenings plaguing the region.
One night, Harriet gives Ruben a ride, and is called to the scene of a burning barn, where she attempts to save a bull but cannot. Meanwhile, Mackenzie, who is on a date with Wayne, a local deputy, witnesses a car speeding from the barn and follows it into a wrecking yard. A crash ensues, and two men are apprehended for the arson, a move meant to stir fear among the townspeople and create a narrative of danger.
Local publisher Joe Hiatt [Paul Dooley] provides Ruben with background on the cattle mutilations, recounting sightings of strange black helicopters flying over the area. Joe publishes editorials about the events, which alienate him from the town’s power brokers and deepen the tension between the local press and the authorities. The town’s dynamics become more tangled as the cattle losses attract attention from various quarters, including the town’s cattle baron, Ben Morgan [Hoyt Axton], who looms large in local affairs.
Ruben, initially reluctant, grows increasingly fascinated by the unfolding mystery. After a relapse, he visits Harriet and makes a crude advance, but she rebuffs him. He leaves and spots a grain mill truck driving erratically, chasing it to a fenced industrial complex that hints at something hidden and ominous beneath the surface of Buffalo’s quiet exterior.
The next morning, ranchers bring a mutilated cow to the police station, intensifying the case. Ruben investigates Joe’s connection to the events and learns that the fenced complex is an abandoned military outpost. Joe’s death soon follows, officially attributed to a heart attack, but the timing fuels the suspicion that something larger is at work.
Harriet sends tissue samples to a New York pathologist, who reveals the cattle organs are riddled with a botulinum-bacteria strain that appears to have been modified via gene splicing. The pathologist notes that such findings echo government germ-warfare experiments from 1969, suggesting a chilling motive behind the mutilations. Meanwhile, Ruben covertly visits Ben Morgan’s ranch and witnesses a black helicopter landing; mercenaries led by Steele threaten Ben, who is being pressured by his nephew, a Washington, D.C. politician, to allow his cattle to be used for experiments. The warning underscores the political and corporate pressures surrounding the affair and sets Ruben on a more dangerous path.
That night, Ruben returns to Ben’s ranch and begins sabotaging equipment used to procure cattle. He is pursued by a helicopter, but manages to elude capture by hiding in a cattle corral, a tense reminder of how exposed everyone is to the covert operation.
The following morning, Ruben arranges for Mackenzie to fly back to New York, but she is abducted by mercenaries before boarding. Ruben then confronts Ben at his office, finding him mysteriously ill and vomiting blood. He forces Ben to drive him to the ranch, but the vehicle crashes and Ben stumbles onto the road, where his abdomen bursts open in a shocking and fatal turn of events. Harriet arrests Ruben for kidnapping, yet she insists to her superiors that both Joe and Ben were murdered because of their knowledge of the cattle experimentation.
An operative visits Ruben in jail, warning him that if he remains silent for 24 hours, Mackenzie will be spared. The stakes rise as Ruben and Harriet flee to the military outpost and manage to sneak inside. A large force converges on the complex, and Ruben holds Steele at gunpoint while Harriet locates Mackenzie. In the rafters of the warehouse, Steele stabs Ruben; Ruben fires back, killing Steele, who falls to his death. Peck and several other operatives open fire, and the trio escapes on foot as the attackers pursue. Outside, vigilantes and police shoot at one of the helicopters, bringing down a lifter that is lifting a dead cow. In the end, the townspeople, Ruben, Harriet, and Mackenzie watch as the remaining helicopters retreat into the distance, their quiet town forever altered by the hidden war that had been waged beneath Buffalo’s surface.
