Like most ghost stories that are also urban legends, the story of the phantom hitchhiker varies from region to region and person to person.
However, like most urban legends and folklore, the story remains roughly the same-
While driving through a dimly lit (or rural, in some cases) area of town a driver happens to find a person attempting to hitchhike. Often times the weather is bad or visibility is poor. Even though the driver rarely stops for hitchhikers, he or she feels compelled to do so in this case.
The person standing on the side of the road often looks out of place. The clothing is wrong, or the person seems too young to be out so late (sometimes the person is a child), or they look to be ill. The driver pulls over and lets the stranger into the car.
Frequently, the driver later recalls that the passenger seems to be particularly quiet. Not rude, but not very forthcoming with any details other than their first name and the address they’re trying to reach. Or, they are interested in telling the driver about how they need to be a party, are visiting family, or other trivial details that the driver doesn’t really need to know but the conversation is pleasant just the same.
If the passanger has been talking, eventually they fall silent. So silent in fact that the driver looks over and realizes that they’re in the car alone. Sometimes the hitchhiker leaves an item behind- a book, a scarf, a toy. Often the driver remembers where they last noticed the passanger being in the car because something startled them, or there was some other event that made them take notice- a deer crossing the road in front of a cemetary for example.
The driver is understandably spooked and is compelled to look into the case further, discovering that a fatal accident occurred at the spot the ghost disappears from the vehicle. In some cases they feel compelled to return the item that was left behind to the address the ghost gave them, only to find out that “Billy” or “Mary” was the name of a child who was killed years before in a car accident while going to a dance or coming home from work.
The driver, understandably frightened, realizes that they have had a brush with afterlife and is adamant for years after the fact that the ghost was in the car with them.