In an alternative version of 18th-century England, Mendelion is ruled in name by a mad Duke, in reality by a group of competing Guilds, and in aspiration by a variety of royal pretenders. Since the Realm was shattered, the king deposed, and the parliamentarians and monarchists locked in struggle, with the Guilds in between, there has never been real peace, and open warfare is just a wrong move away.
Into this tinderbox comes Mosca Mye, an orphan who has taken up with a smooth-talking con man, both because she loves words, and because she accidentally set her mean uncle's mill on fire. Together they get involved in the power intrigues of the city. But Mosca, though very bright and literate (a rarity in this world), understands a lot less than she thinks she does.