Newlyweds Dick (Thomas Jane) and Gina (Lauren German) decide to head across the Nevada desert for their honeymoon, driving at night to beat the heat. Before they head off, a Chris Browning warns Dick to be careful, as couples have been known to get lost, and to stick to the Interstate. Shortly afterward, they realize they are heading the wrong way and veer off onto a different road. Dick turns off the car headlights to drive by starlight, and Gina masturbates herself to orgasm as they press onward through the vast, quiet desert.
When Dick switches the lights back on, he swerves to avoid a figure in the middle of the road. They stop to investigate and discover a man badly injured from a car crash. With no phone signal, they decide to drive him to a hospital themselves, only for the road to come to a sudden end a few miles ahead.
The ride grows tense as they argue, and the injured man awakens with a scream. He asks Gina for a cigarette, urges her to leave her husband, and becomes increasingly erratic, even attempting to strangle Dick and nearly sending the car off the road. Gina intervenes and the two men tumble from the vehicle, continuing the fight until Dick finally beats the stranger to death with a rock. The grim task of disposal follows: they bury the body in a shallow grave, and Gina fills the hole while Dick, searching her handbag, discovers a revolver.
Their trouble isn’t over. They reach a rest area where several cars are parked, and they tidy themselves up while they argue again. Dick discovers he has lost his watch during the burial, and Gina stays behind with the gun while Dick goes back to retrieve it. Returning to the site, he finds the grave empty and gunshots echo across the desert. Gina is missing, and nearby he stumbles upon a grave for a woman as the other cars sit rusted and dust-covered.
Panic sets in as he flees and nearly collides with a deputy sheriff. In the back of a police car, he rides with the deputy to a crime scene where authorities excavate murder victims from a mass grave surrounded by abandoned vehicles. The deputy explains that this is where the rest area had stood 30 years before. Dick recognizes the spot as the place where he buried the stranger. As he watches from the back of the patrol car, a deputy exhumes Gina’s body and finds Dick’s watch. Dick fights his way out of the car and escapes in one of the nearby vehicles, leading the pursuing squad across the desert.
Driving with the lights off, he loses the pursuing cars, but a swarm of insects swamps the road and causes a rollover. Thrown clear of the wreck, he is then almost run down by another car before he passes out. Some time later, Dick wakes to find himself in the back of his own car, listening to a heated argument between him and Gina, and realizes that he was the mysterious stranger he fought and murdered earlier in the evening, screaming at this.