Since I don't know the exact story, I can't say for sure. But generally in a ghost story, elements could include the setting, like a dark forest or an old abandoned place. Maybe in this story, the place where the humper monkeys live could be such a setting.
Once upon a time, there was a strange humper monkey in a forest. One night, a hiker saw the monkey but as he got closer, it vanished like a ghost. He thought it was just his imagination. But then, he heard strange noises that sounded like the monkey. He got scared and ran away, never to return to that part of the forest again.
Since I don't know the story, I can't say for sure. But generally, in a ghost story, elements could include the appearance of the ghost (in this case, the humper monkey), the place it haunts, and the reason for its haunting.
The unknown nature of the humper monkey in the story makes it spooky. It's something that people don't understand, like why it's a ghost or what it wants.
The '12 monkeys story' is about time travel. A man is sent back in time to try to stop a virus from wiping out most of humanity. He has to deal with various challenges and mysteries along the way.
Once I went to the zoo and saw a group of monkeys playing. They were jumping from one branch to another, and one little monkey was trying to steal food from its mother. It was really funny.