Sir Dennis Darby has been murdered, the Automaton has been destroyed, and Sarah Stanton has turned her back on a life of privilege and comfort to try and find her way in the unforgiving streets of New York. But Lord Eschaton, the villain behind all these events, isn't finished with her yet. His plans to bring his apocalyptic vision of the future to the world are moving forward, but to complete his scheme he needs the clockwork heart that Sarah still holds.

But she has her own plans for the Automaton's clockwork heart—Sarah is trying to rebuild her mechanical friend, and when she is attacked by the Children of Eschaton, the man who comes to her rescue may be the one to make her dreams come true. Emelio Armando is a genius inventor who had hoped to leave his troubles behind when he and his sister left Italy for a life of anonymity in the New World. Now he finds himself falling in love with the fallen society girl, but he is rapidly discovering just how powerful the forces of villainy aligned against her are, and that fulfilling her desires means opening the door to a world of danger that could destroy everything he has built.

The Society of Steam takes place in a Victorian New York powered by the discovery of Fortified Steam, a substance that allows ordinary men to wield extraordinary abilities and grants powers that can corrupt gentlemen of great moral strength. The secret behind this amazing substance is something that wicked brutes will gladly kill for, and one that Sarah must try and protect, no matter what the cost.