The Tainted Cup by Robert Jackson Bennett

A peculiar crime. A brilliant investigator. A mystery of epic proportions.

In an opulent mansion at the borders of the Empire, an Imperial officer lies dead - killed when a tree spontaneously erupted from his body. Even here, where contagions abound and the blood of the Leviathans works strange magical changes, it's a death at once terrifying and impossible.

Called in to solve the crime is Ana Dolabra, an investigator whose reputation for brilliance is matched only by her eccentricity. At her side is her new assistant, Dinios Kol, an engraver, magically altered to possess a perfect memory.

Soon, the mystery leads to a scheme that threatens the safety of the Empire itself. For Ana, all this makes for a deliciously thorny puzzle - at last, something to truly hold her attention. And Din? He'll just have to hold on for the ride.