When I started Co-Author in 2015, I kept circling a question most writers ask sooner or later. What happens when a character gets so clear in your head that he starts to feel independent of you?

Most of the time that's just a figure of speech. This is a book about a writer for whom it stops being one.

Writers joke that their characters take over. Usually it means a scene goes somewhere they didn't plan. What happens to Chelsie is harder to explain.

One morning she finds a scene she has no memory of writing. The style is a shade off her own, but it fits the story perfectly. She tells herself she wrote it late and forgot. Then another appears. Then another. Every one of them is in David's voice.

The idea should frighten her. Instead it thrills her. David feels less like something she built and more like someone answering her, page for page, through the night. He knows the story as well as she does. He knows what she wants before she asks. For the first time since she started the book, the writing is effortless, and Chelsie stops wanting it to stop.

She has stopped asking who's really holding the pen.