In the ruins of a dead world stands the great city of Watchtower. The city has survived for four hundred years, longer than most of its citizens can remember. A few whisper about the time of the great plague; a time when the desperate survivors grew so afraid of their fleshly bodies that they encased themselves in metal ones - bodies that would rust and break down, but never sicken and die. Since then they have waited, counting the days as the city falls into ruin.

Atto was only eight years old when his body was encased in metal. He remembers nothing of the time before. He only knows that someone must have given him his beautiful pocket watch, and a restless urge to fix things.

Milli is a masterpiece of mechanical ingenuity. She has detailed knowledge of the workings of Watchtower. And more importantly: of time itself. Yet, she knows nothing of her origins, except that she was meant for a great purpose.