I found some urban legends online.
I'm gonna post some of them :)
This is 'The Knife in the Briefcase':
ONE SUMMER day in Southampton, New York, a woman pulled into a gas station. As the attendant pumped gas, the woman told him she was in a hurry to pick up her daughter, who had just finished an art class in East Hampton.
A very-well-dressed man walked over to her car and started talking to her. He explained that his rental car had died, and he needed a ride to East Hampton for an appointment. She said she would be happy to give him a ride. He put his briefcase in the backseat and said he was going to the men's room quickly.
The woman looked at her watch and suddenly panicked. She drove off quickly, having forgotten that the man was coming back to the car for a ride.
She thought nothing of him again until she and her daughter pulled into their driveway. She saw his briefcase and realized she had forgotten him! She opened the briefcase looking for some form of identification so she could notify him about his belongings. Inside she found nothing but a knife and a roll of duct tape!