While transporting a car from Chicago to San Diego, Jim Halsey picks up a hitchhiker named John Ryder, who claims to be a serial killer. After a daring escape, Jim hopes to never see Ryder again. But when he witnesses the hitchhiker murdering an entire family, Jim pursues Ryder with the help of truck-stop waitress Nash, pitting the rivals against each other in a deadly series of car chases and brutal murders.