This is a complicated story, and not easy to summarize without spoiling the plot. It's made up of murder, blackmail, family secrets, abduction, light romance, police procedure, and courtroom drama, with a nod to the classic Jane Eyre.
This book is advertised as "A Golden Age Mystery", but that is not quite accurate. Though there is a mystery, this is actually a crime novel of suspense and adventure, with elements that are not at all typical of a Golden Age Mystery. It is well-written, intelligent, and, while over-the-top at times, absolutely absorbing.