Numo is a small and loyal homunculus-a synthetic servant born of alchemy and mandrake root. By design, he should think only of his masters' needs. But instead, he can't stop thinking about Hammerfist. Hammerfist is a lady battle-homunculus, much larger and with much sharper appendages, made for the bloody contests of the sporting arena. She has eyes like the purest embers, a mane like a sea of moon-glitter, and, Numo discovers, a horrible brain disease that is eroding her sanity. He is desperate to help, but presents of flowers and tree sap aren't enough. She needs a way to get out of the arena. She needs a revolution. Numo only wishes he knew what a revolution was. But it doesn't matter. If it will save Hammerfist, he'll do anything. Except, of course, the things he doesn't know he's supposed to do. Things like keeping the revolution a secret.