Predator! Predator city! Six miles and closing! Leave it behind! Let's go! Leaving!

Many thousands of years in the future, Earth’s cities roam the globe on huge wheels, devouring each other in a struggle for ever diminishing resources. On one of these massive traction cities, the old London, Tom Natsworthy has an unexpected encounter with a mysterious young woman from the wastelands who will change the course of his life forever.