Quick: Name the shortest horror story you’ve ever read.

Done? If you’re like many people, this probably came to mind:

‘The last man on Earth sat alone in a room. There was a knock on the door…’

This tiny, Twitter-sized tale – Fredric Brown’s ‘Knock’ – is possibly the world’s most famous short horror story. Although it’s a condensed version of a longer (though not by much) story, the two-sentence version is a masterpiece of lean, efficient storytelling. So much is said, and implied – in just two sentences and seventeen words – that it becomes one of the best examples of ambiguity in fiction.

In my opinion, what makes ‘Knock’ so memorable (aside from its length) is that while it sets up an entire fictional world, it doesn’t tell us anything about it or who is outside the door. What happened to the planet? Why is there only one man left? Did everyone else die off? Did they evacuate and leave him behind? Likewise, who or what is knocking? An alien? A demon? An angel? A large duck? We don’t know, and like every great horror story, ‘Knock’ forces us to rely on our imagination to fill in the blanks, creating things more terrifying than anything Hollywood’s CGI maestros or an author’s prose can bring to life.

Not revealing the evil force menacing a character is a simple concept, but as countless horror tales have proven over the centuries, it can be chillingly effective.

The Takeaway

When writing a horror story (or a mystery/thriller) consider never revealing who, or what, is menacing a character or a group of characters. For extra points, leave this entity’s motivations ambiguous, such as if it’s malevolent or just neutral/curious.