In a terrifying and brutal future world, cities are mounted on giant wheels. They hunt each other to the death. Aboard London, lowly apprentice Tom Natsworthy longs to be part of the next attack. When he saves his chief from a mad assassin, he is suddenly flung from the speeding city with a mysterious scar-faced girl. They must run for their lives through the wastelands, tracked by an unstoppable cyborg programmed to kill them...