Persistence vs chance

A couple of decades ago I read an SF/horror short story that scared the hell out of me. So much so that the memory of the story stayed with me, nagged at me. Recently I decided I wanted to track it down again and re-read it, to see if it really was as good as I remembered. That’s when the trouble started. I knew the plot—which to avoid spoiling the delights of the story, I won’t discuss further—but I didn’t know the author, or the title.