What makes a ghost story scary?

Roald Dahl is famous for children’s stories such as Charlie and the Chocolate Factory and James and the Giant Peach…but he was also a big fan of ghost stories, even putting together a compilation written by many different authors called Roald Dahl’s Book of Ghost Stories. In the introduction, he describes the ingredients of a good ghost story:

“The best ghost stories don’t have ghosts in them,” he writes. “Or at least you don’t see them….If a story does allow a ghost to be seen, then he doesn’t look like one. He looks like an ordinary person.”

The same can be said about the movie “Jaws”, where the ghost isn’t a ghost at all…but a shark. We don’t see the shark well at all until well over an hour in, and it’s the tension our own minds create that made the movie so scary. The funny thing is, they kept the shark out of the movie so much because the mechanicals sharks were prone to malfunctions. A happy accident?

I’m going to try to stick to this rule, but it is hard to do because usually the ghosts are the most interesting characters and you want to explore who they are and why they came to be that way. It’s walking the razor’s edge.