Capturing the Devil (Stalking Jack the Ripper Series #4) by Kerri Maniscalco

In this shocking finale to the bestselling series that began with Stalking Jack the Ripper, Audrey Rose and Thomas are on the hunt for the depraved, elusive killer known as the White City Devil. A deadly game of cat-and-mouse has them fighting to stay one step ahead of the brilliant serial killer - or see their fateful romance cut short by unspeakable tragedy. Audrey Rose Wadsworth and Thomas Cresswell have landed in America, a bold, brash land unlike the genteel streets of London. But like London, the city of Chicago hides its dark secrets well. When the two attend the spectacular World's Fair, they find the once-in-a-lifetime event tainted with reports of missing people and unsolved murders. Determined to help, Audrey Rose and Thomas begin their investigations, only to find themselves facing a serial killer unlike any they've encountered before. Identifying him is one thing, but capturing him - and getting dangerously lost in the infamous Murder Hotel he constructed as a terrifying torture device - is another.