Disco lights flashed pink and green as a Katy Perry song blared out of the speakers.
Payton Leutner, 11, and her two best friends, Morgan Geyser and Anissa Weier, were having a ball as they glided around the roller rink.
It was Morgan’s 12th birthday and soon they’d be heading back to her place in the suburban town of Waukesha, Wisconsin, USA, for a sleepover.
It was an evening Payton, who everyone called Bella, had been excited about for weeks.
Morgan and Anissa had been looking forward to it as well – but for very different reasons.
Five months earlier, the two girls had discovered Slenderman. A fictional character, he was tall and thin, wore a black suit and had a blank face.
He’d been created as part of an online competition to create a scary new paranormal character.
His terrifying shadow started appearing in fan fiction and memes all over the internet, and soon he went [viral].
Stories depicted him lurking in playgrounds and stealing children.
The more Morgan and Anissa read about Slenderman, the more the line between fact and fantasy began to blur for them.
Terrified of the character, the girls became obsessed with the idea of trying to keep him happy.
And there was one thing they believed would ensure their safety.
Committing a murder in his name to show their loyalty.
The girls began to plot together and quickly decided on their victim.
Initially, they’d planned to kill Bella at that night’s slumber party after she’d fallen asleep.
But then Morgan changed her mind.
“I wanted to give her one more morning,” the girl later recalled.
Instead, the next day, after breakfasting on doughnuts and strawberries, Morgan, Anissa and Bella headed into the woods nearby to play.
Once they were hidden in the trees, they pounced.
Pushing Bella into a public toilet block, they smacked her head against a brick wall.
But then Morgan got scared.
“Let’s play hide and seek,” they suggested.
Bella agreed, putting their behaviour down to high jinks.
As Bella walked ahead, Morgan showed Anissa the steak knife she’d stolen from her parents’ kitchen and stuffed down her trousers.
This time, there was no chickening out.
Morgan tackled Bella to the ground from behind.
“You do it,” Anissa encouraged. “Go ballistic. Go crazy.”
“I’m so sorry,” Morgan whispered in Bella’s ear before launching a frenzied attack.
“I trusted you,” Bella managed to splutter.
They stabbed their friend 19 times in the legs, arms, and chest.
Then they ran off, leaving Bella for dead.
But they underestimated Bella’s determination to live.
Pulling herself onto all fours, the high school pupil crawled out of the woods onto a road where a cyclist found her weeping and covered in blood.
She was rushed to hospital where she identified her attackers before undergoing emergency surgery.
Her surgeon said if one of the knife wounds had been the width of a human hair further, she would have died.
Meanwhile, cops tracked down Morgan and Anissa.
In separate interrogations they both admitted what they’d done but gave detectives conflicting accounts.
Morgan said the plot to kill Bella was Anissa’s idea. Anissa said it was Morgan’s.
Morgan said she felt calm and that the attempted killing, “didn’t feel like anything”, while Anissa claimed she was “on the verge of a nervous breakdown”.
When asked to describe the attack, Morgan simply repeated the words: “Stabby stab stab stab.”
Anissa told police it was as if they’d been lionesses chasing down a gazelle.
The girls were consistent in one thing they told the police, though.
It was Slenderman who’d made them do it.
Morgan said she believed she had to kill Bella.
If they didn’t, the sinister Slenderman would kill their families.
She said she saw him in her dreams and that she was prone to “Slender sickness” because of “Slender radiation”.
Police discovered 50 terrifying sketches of Slenderman in Morgan’s bedroom.
One showed a girl who was armed with a scythe, standing over a dead girl, while saying: “I love killing people.”
They also found a supplies list for the day of the killing, which included “map of forest” and “kitchen knife”, as well as a mutilated Barbie doll with Slenderman’s symbol – a circle with an X through it – etched into its stomach.
The court treated both of the girls as adults, charging them with attempted first-degree intentional homicide.
Attempts by their lawyers to have them tried as juveniles failed because of the vicious nature of the crime.
Morgan was later diagnosed with schizophrenia, a mental illness that runs in her family.
Anissa was diagnosed with schizotypy, the inability to differentiate between reality and fiction.
As a result of these findings, both girls have pleaded not guilty by reason of mental disease or defect.
They are both facing trial later this year and if found guilty, face up to 65 years in prison.
Bella is recovering well from her horrific ordeal.
When asked how she found the strength to crawl out of the woods, she said simply: “I wanted to live.”
But while her injuries have healed and she’s back in school, the story of what happened to her that day is now infamous and forever linked to the internet myth. It’s unlikely she’ll ever be able to escape Slenderman.