One day in Wilmington, North Carolina, as the Earth passes through the tail of a rogue comet, Rhea-M, machinery everywhere from auto teller machines to drawbridges spins out of control. Soon, a “Happy Toys” truck with a fiberglass goblin face attached to its grille pulls up at the Dixie Boy truck stop. As the driver, Handy, enjoys a cup of coffee, owner “Bubba” Hendershot calls his short-order cook, Bill Robinson, into his office. In the truck stop game room, a teenage gamer watches in amazement as a pinball machine self-destructs. Packs of cigarettes fly out of the cigarette vending machine, coffee cups spit out of the coffee machine, and coins flow out of a coin-changer machine. The youth pockets as many cigarette packs and as much change as he can carry. As a gas station attendant fills Handy’s truck, the pump becomes stuck. When the attendant examines it, diesel fuel squirts out, leaving him blind. Meanwhile, Hendershot orders Bill to work a nine-hour shift but only clock in for eight. Given Bill’s prison record, he does not have a lot of career options, and is forced to cooperate. Wanda June, the waitress, is attacked by an electric knife. As she fights off the appliance, it falls to the floor, and goes after her shoes. Bill grabs a hammer and smashes the knife. As the teenage gamer leaves with his bounty, a flashing video screen hypnotizes him. The youth grabs a game console handle, and is electrocuted. Bill discovers the teenage gamer dead on the floor. Nearby, a female hitchhiker named Brett takes control of the steering wheel, and forces the driver, a bible salesman, to stop at the Dixie Boy after radio news describes strange, grisly events in town and warns drivers to avoid major highways. The Bible salesman is shocked by Brett’s behavior and salty language. As he lectures her on the importance of good breeding and manners, Handy’s Happy Toys truck starts without its driver. Brett pulls the salesman from the path of the oncoming truck just in time to prevent an accident. After the truck comes to a stop, Handy shows diner employees and customers that he is still holding the keys to his rig. Meanwhile, newlyweds Connie and Curt discover a dead body at a roadside gas station. As Curt follows the trail of blood, a small truck parked in the rear spontaneously starts up. When Curt narrowly misses being hit, he and Connie make a hasty departure. Back at the truck stop, Hendershot orders his employee, Joe, to temporarily store the teenage gamer’s body in the basement. Soon, Bill Robinson investigates Handy’s truck to uncover a reason for its rampage, but finds nothing. Brett interrupts Bill to flirt as radio news reports speak of strange mechanical events happening all around the world. While bicycling home, a Little League ball player named Deke sees dead humans and animals strewn across the neighborhood. News reports adds that no mechanical device can be trusted. Deke hides in the bushes, and watches a driverless ice cream truck go by. He jumps back on his bicycle, and finds himself being chased by a lawn mower. Hendershot orders Duncan not to leave the Dixie Boy until he punches out on the time clock. Duncan wants to find his son, Deke, and refuses to comply. As Duncan walks to his car, he is run over by a semi-truck. The Bible salesman becomes irate when a truck rams into his Cadillac. As he lets off steam, Handy’s Happy Toys truck rams him, and he lands face first in a nearby creek. Suddenly, all the parked trucks drive surround the Dixie Boy like a circling wagon train. On the highway, Connie and Curt narrowly miss hitting a Mack truck. As they recover and continue down the road, the truck chases them, and tries to force them off the road. Curt maneuvers the car such that the Mack truck misses a turn, careens down an embankment, and explodes. When Curt sees a sign for the Dixie Boy, he decides to stop and call police. To get past the circling trucks, Curt waits for an opening and makes his move. As he accelerates toward the diner, a truck clips his car, and flips it over. Curt crawls out, but Connie is stuck. Bill and Brett rescue her, and lead the couple to safety as Hendershot uses a flamethrower to stop the truck from killing them. Later, Bill and Brett discover that Hendershot has amassed an arsenal of weapons in the basement. Although they have no intention of stealing, Hendershot is eager to break up their budding romance, and reveals Bill’s criminal past. Bill is ashamed, but Brett is able to see the new person he has become. Deke travels on foot, but cannot figure out a way to get past the truck convoy surrounding the truck stop. Later, Bill and Brett make love. She theorizes Earth passing through the comet’s tail is causing the mechanical disturbances. If they can stay alive for seven days until the comet passes, they will survive. Bill wants to escape on a sailboat to Haven, a nearby island, where motor vehicles are prohibited. Brett likes his plan. Soon, the Bible salesman regains consciousness in the creek and begins howling. Meanwhile, Deke finds a culvert that runs underneath the road to the truck stop. As he wades through muddy water in the pipe, he can hear trucks driving along the road. Bill and Curt take guns and supplies from Hendershot’s arsenal, and escape through a sewer drain in the truck stop bathroom. When Deke arrives at the creek, the Bible salesman grabs his arm and demands to be rescued. Bill and Curt find Deke, determine that the Bible salesman has died, and scramble when a truck chases them. Bill, Curt, and Deke disappear into the sewer drain, and back to the safety of the Dixie Boy. When another truck tries to chase them, Bill destroys it with a flamethrower. Hendershot breaks the news that Deke’s father, Duncan, is dead. Bill holds Deke tight as he mourns. In the morning, the trucks outside come to a halt when a front loader, and a machine gun-mounted railroad pump trolley appear. The front loader pushes Hendershot’s parked car into the diner. When Hendershot retaliates with his flamethrower, the machine gun fires into the eatery. Hendershot is killed and the others run for cover. Once the shooting stops, Wanda June grabs the flamethrower and walks outside. The machine gun shoots her, but she destroys one truck. The horn on the front loader starts tapping out Morse code. Deke deciphers a message that the machines need more fuel but there is no electricity. Suddenly, the power turns on and Bill switches on the pumps. Everyone takes turns filling up gas tanks. More trucks arrive to refuel. When Bill announces that there is no more gas, the trucks sound their horns in protest, and survivors go back to the diner to rest. In the morning, Bill lobs a grenade at the machine and destroys it. After dark, he leads the survivors through the culvert to the other side of the highway. They watch as a truck crashes into the Dixie Boy game room. Other copycat trucks follow, destroying different parts of the building. A fire sets off Hendershot’s basement arsenal, and levels the complex. The survivors disappear into the woods, heading toward the marina. The Happy Toys truck follows the group, but Bill uses the flamethrower to incinerate it. The survivors commandeer a sailboat, and Bill promises Deke that they will be safe on Haven Island. Two days later, a Russian military space ship disguised as a weather satellite destroys an unidentified flying object, and after six days, the Earth completes its orbit past the tail of the Rhea-M comet.