London, 1887. Victorian adventuress and butterfly hunter Veronica Speedwell receives an invitation to visit the Curiosity Club, a ladies-only establishment for daring and intrepid women. There she meets the mysterious Lady Sundridge, who begs her to take on an impossible task—saving society art patron Miles Ramsforth from execution. Accused of the brutal murder of his artist mistress Artemisia, Ramsforth will face the hangman’s noose if Veronica cannot find the real killer.

But Lady Sundridge is not all that she seems, and unmasking her true identity is only the first of the many secrets Veronica must uncover. Together with her natural historian colleague Stoker, Veronica races against time to find the true murderer…