There are few thoughts as scary as being buried alive.
It's something we see in horror movies, a notion so claustrophobic that you really can't think about for more than a few moments.
This is the situation that Barbara Jane Mackle found herself in for over 80 hours.
The 20-year-old student at Atlanta's Emory University had the world at her fingertips. She was tall, beautiful, brunette and an heiress, to one of Florida's wealthiest families.
Her father, Robert Mackle, was the owner of Deltona Corp, one of the region's biggest housing development companies, worth a whopping $65 million. Her brothers also worked on the business and had friends in high places, including the sitting senator at the time George Smathers and the president-elect Richard Nixon, according to Time, who first reported the story when it happened in 1968.
Of Florida's wealthy elite, the Mackle's were the 'big fish'.
On the day in question, Barbara was sitting an exam when she began to feel unwell. She left the exam in a hurry, calling her mum to pick her up. Her mother Jane was in the area as she was about to drive her daughter home for Christmas. It was December 17.
The mother-daughter duo checked into a motel, the Rodeway Inn, and spent the night talking to one another. Barbara's boyfriend Stewart Woodward visited for a while, before driving off in his white Ford.
At 4am, the pair heard a knock on the door. They were told that it was a detective who was reporting a car accident involving a white Ford.
Struck with the terror that Stewart had been in an incident, Jane opened the door. Instead of a police uniform, she was confronted by a man in a mask with a gun and a shorter individual, also in a mask.
They used chloroform to subdue the women, binding Jane and grabbing Barbara.
Jane managed to free herself and alert authorities, but Barbara was already spirited away. She would end up 30 miles north of Atlanta, facing a very grim reality.
Meanwhile, her family went into action.
After being sent a ransom request for half a million dollars, her father Robert moved fast to pay the fee and free his daughter.
He filled a suitcase with $500,000 and dropped it off near the Biscayne Bay, where it was to be picked up by the kidnappers. However, a local resident called police upon seeing the unfamiliar boat pull up, fearing that it was another burglary, as they'd plagued the area.
Police arrived to find 'two men' carrying the suitcase, and when they were spotted, they dropped it and escaped.
With the ransom payment foiled, Robert immediately began planning a second drop. But now, detectives had another clue: a blue Volvo at the scene of the first pick up that was registered to a marine scientist, George D. Deacon.
He worked at the Institute of Marine Science, where the boat had been stolen.
On the second attempt to drop the money to the kidnappers, Robert was successful. For 12 hours, the family anxiously waited for Barbara to be freed.
At the end of the week, Barbara was found, having been located in a box buried 45 centimetres underground in Gwinnett County, Georgia.
The box was described as 'coffin-like', however her kidnappers had provided food, water and sedatives, as well as two venting tubes. A provided light broke early on, pitching Barbara into darkness. She was there for three-and-a-half days. Over 80 hours in total.
Barbara later wrote a book about her experience, called 83 Hours Till Dawn, in which she said, "I screamed and screamed.
"The sound of the dirt got farther and farther away. Finally, I couldn't hear anything above. I screamed for a long time after that."
She thought about her upcoming family Christmas to keep her thoughts from wondering anywhere too dangerous.
Barbara was found in good condition, despite the horror she had been through, and was flown to her parents' home in Coral Gables, Florida, where she would finally get to celebrate the Christmas that had kept her going.
Meanwhile, the FBI were zeroing in on two individuals. Warrants went out for Gary Steven Krist, 23, a Californian convict who had been using George D. Deacon as an alias.
His accomplice was Ruth Eisemann Schier, 26, a short blonde woman at just 5'3". It's believed that Jane Mackle had assumed she was a younger boy due to her height.
Krist was later found off the coast of Florida, while Ruth Eisemann Schier was arrested when her prints turned up a positive match. She had been applying for a job at a hospital in Oklahoma. Schier was deported back to Honduras.
Krist was given life in prison but only served 10 years, going on to be a licensed doctor in Indiana, according to ABC News.
Barbara went on to continue her life, living in Atlanta, tying the knot and welcoming children of her own.
Feature image: Getty.