Scene of a crime

The other day I took one of my dogs for a walk, and while doing so passed a small park in a fairly quiet neighborhood. My second pass of this park, en route back to my car, seemed a bit odd, mainly because there was a single, small backpack left on the sidewalk near the curb of the road. Given that I didn't notice the backpack on my first pass, and also that it was situated fairly near the empty swingsets, I had the distinct impression that a small child had just been kidnapped moments before.