Original story can be found on Creepypasta.com.
One day at a shopping mall in the afternoon, a woman was coming out of the mall from a shopping spree. She was in a happy mood. She had gotten to her car and loaded her stuff that she had bought into her trunk. When she was done loading, she shut the door of her trunk and she saw an old lady standing by the passenger side of her car.
“Would you be a darling and give me a lift home? I don’t have a car and I was walking all day,” the old woman said.
“I’d be happy to,” the woman said, unlocking the door for the old woman.
As the shopper started to make her way around the car to the driver’s side, she started to feel uncomfortable. So when she got in the car, she looked in her purse and said, “Darn, I can’t find my credit card. I’m going inside to see if anybody found it.”
“I’ll wait for you here,” the old woman said.
The woman left to go look for help. Then she found a security guard and told him the situation.
They went back to the woman’s car and the passenger door was wide open. On the seat of the car was a shopping bag that the old woman had been carrying. Inside of the bag was the old woman’s dress and a gray haired wig, along with a huge butcher’s knife, a video camera, and a roll of duct tape.