Violet Sainteclaire has never been to London, but when she arrives, she has a sense that something is very wrong. It is 1890, and London is locked in a vicious war between the Legion and the outlaw Boomslang: a war which, if history has any say, is not meant to exist.

She is a Harbinger: a servant of the omniscient Fate, and Violet is tasked with righting the course of history. Following Fate’s orders, Violet is given a simple task: aid the Boomslang. To do it, she joins the rebellion, the only force capable of toppling the authoritative regime who controls the British Empire. As the war comes to a head, Violet and her friends (a witch-cat, a rebel-leader with a flair for danger, a cutthroat socialite, a mermaid, and a fabricated-human) are forced to decide who must live, and who must die, to put the earth back on track.