What would happen if the world ran out of water? Would our societies survive? Would our technology? The more I thought about this, the more complex the situation became. Without water, humans and animals would get sick, cities crumble, and the way of life we know would disappear. At first I set the book in the real world. I started doing research about how people would survive in a dystopian land, which technologies would last, and which would not, but I soon got bogged down in the details. What I needed was an alternative world and a history which is based on ours, but is nevertheless a fiction. This was my starting point, but the book took off when I found my main character. As is usual for me, she came in one vivid image -- a girl standing on a rock looking down on a line of wagons carrying water to a distant town. So precious is their cargo that the wagons are guarded day and night. Mouse wants to be a guard. She wants to leave the narrow confines of The Town and go out in...