Captain-turned-criminal Jacob Burn is the unlikely survivor of two zepliner crashes. The first destroyed his career as a pilot, disgracing his nobleman father and ending his life of privilege. But the second threatens to destroy Burn's whole world-Veridon, an ancient terraced city reborn through The Church of the Algorithm's recent advances in mechanics, technology, and cog-work.

Moments before the Glory of Day wrecked, a former underworld associate of Burn's handed him an unusual and complicated cog for safekeeping. But the artifact-cog quickly draws Burn unwanted attention-too much of it, from too many of Veridon's most powerful factions, casting doubt on even his closest allies.

A far more dangerous and unpredictable enemy has also joined the manhunt, carving a bloody trail across the city, while Burn's frantic search for answers only leads to more questions. At the heart of it all, the mysterious cog, which hides a secret potent enough to shake Veridon to its very core, and recast Burn's entire existence.