Harriet Beecher Stowe thought Uncle Tom's Cabin was written through her by Another Hand, so little did she know what was going to happen from moment to moment in the book. She herself was amazed at what she was writing.
Sophy Burnham (2011). “For Writers Only: Inspiring Thoughts on the Exquisite Pain and Heady Joy of the Writing Life from Its Great Practitioners”, p.18, Penguin