One morning when my daughter was very young, I took a new box of her favorite cereal out of the cabinet and brought it to the kitchen table. As soon as I put the box down it began to shake, and the bag inside began making rattling sounds.
These were not little creepy shakes or sounds. These were mouse-size shakes. Or maybe rat-size sounds.
My apartment didn't have mice or rats, but I carefully checked the outside of the box anyway, and found it completely intact and sealed. I checked the label to see if there was some sort of wind-up toy prize included inside that was going off on its own -- and there wasn't. Whatever was in the box was inside the cereal bag, and sounded as if it were trying to chew or claw its way out.
I put the box in a garbage bag, tied off the bag, carried it downstairs and tossed it into my building's Dumpster. I then consoled my kids (especially my daughter, who was quite put out that Mommy threw away her favorite cereal) with a trip to our favorite pancake restaurant for breakfast.
At the time I thought I did the sensible thing by playing it safe and just getting rid of it immediately. I was by myself with the kids and I might have let something nasty loose in my apartment, or maybe gotten myself bitten. Yet later that same day I started wondering -- just what could have gotten into that box? How? Where -- at the factory? Had to be a mouse. Or a rat. Finally I couldn't stand it another minute, and went downstairs to grab the trash bag out of the Dumpster. By that time it was gone because that was pick-up day.
I'll never know what it was, and seven years later, I still think about that damn box of cereal.
How does this apply to writing, you ask? Well, my unidentified cereal box occupant is a bit like every story waiting to be written outside your comfort zone. You don't know what it is, only that it's inside you, and it's trying to get out. Open up and you don't know what you might let loose. Look or reach inside for it, and there's a chance you may get hurt.
But throw it away without taking a look, and you'll always wonder.
Somewhat related link: David Niall Wilson's post Writing on the Edge - The Fiction Valence Coefficient.