In the north of England, Hadrian's Wall once formed the northern frontier of the mighty Roman Empire, guarding it from the wild tribes (and, some say, less mundane horrors) beyond. However, by these enlightened days of the mid-nineteenth century, it has long since crumbled to a mysterious (if still striking) ruin. As amateur archaeologists (NOT treasure hunters, despite the slurs of some newspapers) you were excited to be invited by one of the local landowners to make the first scientific excavation of Vercovicium, a fort on his property. You could've wished that he seemed more interested in history and less in one-upping his neighbour, but you began with enthusiasm. This has only been slightly tempered by the strangely vivid dreams you've had of Roman times and the increasingly lurid rumours of a (naturally unrelated) series of grisly deaths amongst local people and livestock.

London, 1924. Rumours abound in polite society about the Cosmopolitan Bookshop and its reclusive owner Edwin Chalmers. It is said that he can obtain any book for a price, no matter how esoteric or depraved its content. When a rare book is reported missing from the Bookshop's shelves, the ladies of Smythe's Discreet Investigations, London's first all-female detective agency, are surprised to be asked to look into it.