In May 2014, Morgan Geyser and Anissa Weier stabbed their friend Peyton Leutner 19 times in a forest in Wisconsin to please the fictional internet-horror character Slender Man. However, Peyton survived the attack and was saved by a biker who saw her crawling through the forest.

Morgan was sentenced to 40 years in a psychiatric hospital, while Anissa only received 25 years. In 2021, Anissa was granted a supervised release, while Morgan was granted a conditional release to a group home in early 2025.

In November 2025, Morgan successfully cut off her ankle monitor and went missing near Madison, Wisconsin. She was found the next day and was taken back into custody.