Grace Andrews and Jim Halsey are tormented by a mysterious hitchhiker named John Ryder, a.k.a. The Hitcher.
The young couple hit the road on route to spring break. Ryder dangerously stands on the road, near his car, which apparently has broken down. After passing they worry that they might have hit him. When they see that he is unharmed, Grace insists that they do not give him a ride as he could be dangerous.
Later they arrive at a gas station. After Grace decides to go to the bathroom, Jim fills up his car and sees Ryder climb out of a tractor-trailer cab. After going inside, Ryder comes back out and begins using the phone. Ryder introduces himself and asks for a ride. Reluctantly Jim agrees...(from wikipedia)
Just loved that movie. If you have some free time - watch it :))