Shelton, Paige. Scottish bookshop mystery series #8

"Bookseller Delaney Nichols receives a mysterious cloaked visitor who 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 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, the contents of Shelaigh's vast library, and an unspecified sum of cash. Delaney is also wary, because Shelaigh was known in the 70's for various hijinks, and was even suspected (but cleared) of murder. When several homes in Edinburgh are robbed in a manner reminiscent of Shelaigh's old tricks, and a man connected to her is killed, people naturally suspect Sheilagh, but she herself has disappeared from her home, seemingly kidnapped by the villain."--Publisher