London, 1887. At the Curiosity Club, a ladies-only establishment for daring and intrepid women, Victorian adventuress Veronica Speedwell meets the mysterious Lady Sundridge, who begs her to take on an impossible task--saving society art patron Miles Ramsforth from execution. Ramsforth, accused of the brutal murder of his mistress, Artemisia, will face the hangman's noose in a week's time if the real killer is not found.

But Lady Sundridge is not all that she seems, and unmasking her true identity is only the first of many secrets Veronica must uncover. Together with her natural-historian colleague, Stoker, Veronica races against time to find the true murderer. From a Bohemian artists' colony to a royal palace to a subterranean grotto with a decadent history, the investigation proves to be a very perilous undertaking indeed....