In a part of the city called the Downside, Randal and Jackson live as far as they can from the Corvidae, the mutated crow-gangs who roam the streets. Jackson is a patchworker, able to fix badly injured people by adding clockwork appendages. Randal is one of the men he helped: now with a clockwork heart, a copper mask, and metal limbs, he is devoted to Jackson but anxious about his own humanity. When a young girl brutalised by the Corvidae lands on their doorstep, Jackson is determined to help her, despite the danger if the gangs find out that she's still alive.