The clock stopped at midnight. Then, I saw a face in the mirror that wasn't mine. I couldn't look away as it started to smile a sinister smile. It felt like it was reaching out from the mirror, its long fingers stretching towards me. I tried to run, but my feet were glued to the floor. I closed my eyes tightly, hoping it would disappear when I opened them again. But when I finally gathered the courage to peek, it was still there, closer than before.
They often play on our deepest fears. Take 'The cellar door opened on its own. Something dark and formless slithered out.' It taps into the fear of the unknown in a very short space. The brevity makes it even more impactful as there's no time for the mind to rationalize. It's just pure fear hitting you.
Some other scary two - sentence stories could be. 'The cemetery at midnight was still. But then the tombstones started to tremble.' 'I was alone in the old library. Suddenly, a book flew off the shelf and landed at my feet.'
Two-sentence horror stories can be quite scary. They often use simplicity and ambiguity to let your imagination run wild, which can make the fear more intense.
The brevity. With just two sentences, they create a sense of mystery and unease. There's not enough space to fully explain what's going on, leaving a lot to the imagination.