Writer-director Egerton said he began researching childhood crimes after the Slender Man stabbing . One of the inspirations for the story was Mary Bell , who had murdered two toddlers when she was a child . Bell had been granted a new identity after being released from jail , but tabloid reporters discovered her new identity . Producers wanted the protagonist to be innocent , but Egerton told them that the story depended on facing one 's past
Slender Man stabbing
Slender Man stabbing
Mercy Black