The hands-down, all-time chart-topping question writers get is, “where do you get your ideas?”

Usually we mutter something jokey and self-effacing about Target or the Idea Elves, because the truth, at least for me, is, we don’t know where ideas come from. They just come…and whether they arrive as an image, or a scrap of dialogue, or a what-if question, it’s hard to say where they’re born.

At least, that’s true most of the time.

But, on Tuesday, I had an idea, that turned into a story (my first-ever horror story!), and I can chart exactly how it happened.

I spoke at an event Tuesday night, out in the suburbs, and I was driving home, letting my trusty GPS be my guide. As I tooled through the darkness, along a deserted road I’d never been on, I thought, What if this thing doesn’t want me to get home?

What if it sends me somewhere else entirely?

On Wednesday morning, I sent out a tweet asking if anyone had ever written a story about a possessed GPS.

A few people mentioned the great Stephen King story, “Big Driver,” (it’s in his latest collection, FULL DARK NO STARS). But in that story, the GPS is a benevolent presence, almost a friend to the troubled heroine.

I was thinking of a darker kind of GPS. And then, I started asking the big writers’ question: why? Why would a GPS want to do bad, bad thing?

Just like that, I had a story. An abused wife. A dead husband who doesn’t want to stay dead. A gift-wrapped box in the attic…and a GPS that starts telling its new owner to make some seriously wrong turns.

This was Wednesday morning. I emailed my brilliant agent and asked, if I write this thing, like, today, is there any chance we can get it up for sale on Halloween?

She talked to my editor. My publishing house swung into action. I wrote the story…and it came really, really fast. Thirty-five pages in five hours fast.

My agent and my editor both gave me notes. I revised it late Wednesday night and Thursday morning (the finished product clocked in at around forty pages, or 10,000 words).

On Thursday afternoon, my copy-editor, Nancy Inglis took a pass. By Thursday night, we had a cover, designed by the amazing Anna Dorfman. Everyone there hustled to get this thing formatted, spruced up, and ready for your enjoyment.

The story goes live on Monday – Halloween – and will be available on Amazon, on B&N and on iTunes for a mere 99 cents -- such a bargain!

Technology is amazing. And my publisher’s great. I hope you have as much fun reading “Recalculating” as I did writing it.

Happy Halloween. And if your GPS starts sounding like it’s angry with you the next time you take a trip, you might want to pack a map…