Bookseller Delaney Nichols receives a mysterious cloaked visitor one evening at the Cracked Spine Bookshop. He presents to her an even more perplexing note: an invitation to an exclusive treasure hunt hosted by eccentric socialite Shelaigh O'Connor. Delaney is intrigued, but also cautious: Shelaigh, while charming in person, has a reputation for her hijinks as a wealthy young woman in the ‘70s. She was even once suspected for the murder of a former boyfriend, though ultimately cleared of all charges.

But Delaney is enticed by the grand prize at the end of the treasure hunt: a highly valuable first edition copy of The Strange Case of Dr. Jekyll and Mr. Hyde, by Robert Louis Stevenson. The winner is also to receive the contents of Shelaigh’s vast library, and an unspecified sum of cash.

The night after the first meeting of the treasure hunters, however, several homes in Edinburgh are robbed in a manner reminiscent of Shelaigh’s old tricks. And when a man connected to Shelaigh is killed, suspicion builds. Except Sheilagh herself has disappeared from her home, seemingly kidnapped by the villain.

Terror mounts throughout the city as Delaney attempts to solve the mystery, while trying to stay out of the killer’s clutches. For she, it seems, is his next target.