While I would love to write my own short description of the plot, I won't in this case since it might prepare you mentally for what you're about to read. I do promise that the summary that you can see on the book will not prepare you enough.
This novella freaked me out. While the plot of many horror novels can be discounted with rational thinking, the plot of this one hits on one of my largest fears (probably the same for most people) and cannot be brushed aside or called unlikely because we don't know for certain. Curran barely lets the book get started before grabbing you by the throat and refusing to let go until the breathtaking conclusion. I can't recommend this one highly enough as it's a novella of the year candidate for me. Read it! You won't be disappointed.