University students Lewis Thomas (Paul Walker) and Venna Wilcox (Leelee Sobieski), Lewis' childhood friend and crush, prepare to go home for the summer holiday. Lewis offers to come by Venna's campus (they go to different universities) to drive her home instead of both of them flying back; Venna happily agrees. Lewis calls his parents to announce the change of plan and learns that his older brother Fuller (Steve Zahn), the family's black sheep, has been arrested once again. Lewis drives to Salt Lake city and bails out Fuller, who then tags along for the trip.
At a gas station, Fuller has a CB radio installed on Lewis' car, and the two begin listening on truckers' chatters. Fuller coaxes Lewis into playing a prank on a truck driver nicknamed 'Rusty Nail' (voiced by Ted Levine (uncredited)). Lewis pretends to be a woman named Candy Cane and sets up a meeting with Rusty Nail in the motel where Lewis and Fuller will be spending the night. Lewis gives him the number of the room next door. The room's occupant is an irritable businessman. When Rusty Nail arrives at the man's room, arguments and sounds of a scuffle are briefly heard. The next morning, Sheriff Ritter announces to Lewis and Fuller that they found the businessman on the highway, still alive with his lower jaw ripped off. Ritter figures out the two are involved in the incident, but lets them go as he's already had his hands full and they don't know anything other than the man's nickname.
On the road, Rusty Nail is heard again on the CB radio looking for Candy Cane. Lewis talks to him and reveals that he is Candy Cane. Rusty Nail demands an apology and Fuller insults him instead. Rusty Nail implies that he already sees Lewis' car and the two begin to panic. At the next gas station, they unsuccessfully attempt to contact Ritter. Seeing an ice truck pulling into the gas station, the already paranoid pair drive away. The ice truck driver chases them down. However, it turns out the driver is merely trying to return Lewis' credit card, which he left behind in panic. The real Rusty Nail then shows up in his truck and crushes the ice truck and the driver. He then slowly pins Lewis's car against a tree. The two hysterically apologize and Rusty Nail drives away, declaring his actions to be simply a retaliatory joke.
Believing themselves to be safe, the brothers arrive at the University of Colorado and pick up Venna. They stop at a motel and drink at a bar. Lewis goes to sleep, but Rusty Nail calls him, revealing he knows of Venna. The three flee from the motel. Rusty Nail contacts them, announcing that he kidnapped Charlotte, Venna's friend. He directs them to a cornfield, where he gets them to split up and kidnaps Venna.
Rusty Nail sets up a meeting at another motel, mirroring the false date he was pranked with. He sets up a trap that will kill Venna if the room door is opened. Fuller attempts to get in the room via a window, but is injured by Rusty Nail and stuck outside the room. Rusty Nail's truck appears uphill and begins rolling down towards Venna's room. Lewis frees Fuller and the brothers save Venna just in time. As the police investigate Rusty Nail's truck, they see a dead body in the driver's seat and Charlotte, still alive, on the floor.
Lewis, Fuller and Venna are treated for their injuries at an ambulance. At this point, the dead man turns out to be the ice truck driver. A CB in the ambulance is on and the group hear Rusty Nail's voice, learning that he is still alive and free.