Escape from Houdini. The Devil's Hunt

Audrey Rose Wadsworth and Thomas Creswell arrived in America — so unlike aristocratic London. But, like London, Chicago has its dark secrets: upon arriving at the world’s fair, the lovers learn about missing people and unsolved crimes.
Trying to help, Audrey Rose and Thomas begin their own investigation and confront a serial killer unlike any they have encountered before. But identifying him is only half the battle; capturing him while not getting lost in the infamous "Castle of Murders," built specifically for the sophisticated killing of victims, is a much tougher task.
Will Audrey Rose and Thomas be able to see this case through to the end, preserving their lives and love, or will luck abandon them when their most immoral opponent delivers the final, deadly blow?