Jim Halsey has to drive a Cadillac from Chicago to San Diego in exchange for a good sum of money. As the trip is certainly boring and monotonous he accepts to take a hitchhiker named John Ryder who tells him that he has just committed a horrible crime on that same road. Terrified by his words, he manages to throw him out of the car … but the nightmare has only just begun, since Ryder chases him to end him and with him who gets in his way. So Halsey can only run for help, like that of the waitress at a roadside bar who will end up suffering Ryder’s madness in her own flesh. For Halsey there is only one escape, to kill this serial killer or let him kill him.