When I start one of these wewrites, I always try to figure out what's the most obvious route to go, and then I try to go another way.

So for this one, I thought the most obvious path would be Nathan opening the door thinking it's his friend Mark, and then upon opening the door, he finds it isn't his friend but it's some killer or thief or someone bad that's there at the door.

So rather than do what I thought most others would do, I switched the focus to Mark rather than Nathan, and although the "something" still happens to Nathan, we see it from another person's viewpoint.

As for adding more to the story, remember, this is my practice contest for keeping posts to around 500 words for my entries, so I basically can only cover what I consider to be the most important points.

When I write my drop in the ocean pieces, I usually write a much longer story or article, with fuller character and background development.