City of the Uncommon Thief by Lynne Bertrand
A dark and intricate fantasy, City of the Uncommon Thief is the story of a quarantined city gripped by fear and of the war that can free it.
"Guilders work. Foundlings scrub the bogs. Needles bind. Swords tear. And men leave. There is nothing uncommon in this city. I hope Errol Thebes is dead. We both know he is safer that way."
In a walled city of a mile-high iron guild towers, many things are common knowledge: No book in any of the city's libraries reveals its place on a calendar or a map. No living beasts can be found within the city's walls. And no good comes to the guilder or foundling who trespasses too far from their labors. Even on the tower rooftops, where Errol Thebes and the rest of the city's teenagers pass a few short years under an open sky, no one truly believes anything uncommon is possible within the city walls. But one guildmaster has broken tradition to protect her child, and now the whole city faces an uncommon threat: a pair of black iron spikes that has the power of both sword and needle on the rib cages of men has gone missing, but the mayhem they cause rises everywhere. If the spikes are not found, no wall will be high enough to protect the city—or the world beyond it.
And Errol Thebes? He's not dead and he's certainly not safe.