Here is one. 'The old house was silent. I heard a child's laughter, but I was alone.' This simple two - sentence horror story creates an immediate sense of unease. The contrast between the expected silence in an old house and the sudden, unexplained sound of a child's laughter when no one else should be there is quite chilling. It plays on our natural fear of the unknown and the unexpected in spooky, deserted places.
It plays on our common fears. Fears of the unknown, of being alone, of the dark. A 'two sentemce horror story' like 'I was home alone. The lights started flickering and I couldn't find the switch' taps into those basic fears and makes us shudder because we can easily imagine ourselves in that situation.
Another really scary one could be 'My phone rang at 3 am. The caller ID said it was me.' It plays on the idea of the self being something other or unknown, and calls at that time are always spooky.
They are concise. For example, 'The phone rang in the dead of night. It was my voice on the other end asking for help.' In just two sentences, it creates a sense of dread. They often rely on the unexpected. Like 'I found a door in my basement that wasn't there before. When I opened it, a cold hand grabbed mine.' It takes a normal situation and twists it into something terrifying.
I think 'The clock stopped at midnight. Then I heard footsteps.' is quite scary. It gives this feeling of something ominous starting right at a spooky time.