Miss Alvermina Holmes, daughter of Sir Mycroft and niece to the famous Sherlock, is summoned to the British Museum in the dark of night. Bored with her scientific experiments, and trying to get something to take her mind off the fact that her mother abandoned her and her father over a year ago, Mina decides to accept the invite.
When she arrives, she finds that another young woman has received the same summons. Miss Evaline Stoker, the younger sister of author and theatre manager Bram, has vampire hunting in her blood, and several illustrious ancestors who hunted the supernatural scourge during the Regency era. Unfortunately for Evaline, there are very few vampires left in England, and despite all her enhanced strength and speed and the training she does, she’s never actually come across one yet. She’s also deeply uncomfortable at the sight of blood, another drawback for any slayer of the undead.
The two young ladies discover that their summoner is none other than Irene Adler, now employed as a curator at the Museum, when she’s not trying to help the royal family sort out tricky situations. A couple young women have been found dead, apparent suicides, but Miss Adler suspects foul play. A clockwork scarab was found in the possession of both the women. A third young woman has disappeared, and Miss Adler has been tasked by Princess Alexandra to do everything in her power to ensure that the girl is found alive. Adler wants to recruit Mina and Evaline as her agents.