In the far future in a space-port the size of a city, Crudrats scrape out a meager living cleaning great machines of the pollution generated by converting dark energy into usable power. Only children can safely traverse the cramped tunnels, filled with mechanical perils–grow too tall or too broad, and they’ll get caught on a blade and killed, or worse. Like rats, they scurry frenetically on their daily errands to clean the crud so their city can maintain orbit, only to face expulsion when they reach puberty.