Bronze Gods (An Apparatus Infernum Novel)

Danger stalks the city of steam and shadows.
Janus Mikani and Celeste Ritsuko work all hours in the Criminal Investigation Division, keeping citizens safe. He's a charming rogue with an uncanny sixth sense; she's all logic--and the first female inspector. Between his instincts and her brains, they collar more criminals than any other partnership in the CID.

Then they're assigned a potentially volatile case where one misstep could end their careers. At first, the search for a missing heiress seems straightforward, but when the girl is found murdered--her body charred to cinders--Mikani and Ritsuko's modus operandi will be challenged as never before. Before long, it's clear the bogeyman has stepped out of nightmares to stalk gaslit streets, and it's up to them to hunt him down. There's a madman on the loose, weaving blood and magic in an intricate, lethal ritual that could mean the end of everything...