...Because I've already posted this as part of a longer story which some of you have read at dueSlash.
But it started out as a short-short, complete in itself, and it seemed to fit the challenge, so I am shamelessly reprinting it here while I think of something original to write. Please don't hang me in effigy.
And even more shamelessly, the whole thing is at:
http://www.dueslash.com/archive/1090.html (Thanks for asking,
theodosia!)
Let's call this
( Ghost in the Machine )