Every Hour Until Then (Timeless, Bk. 5)

As a time-crosser, Kathryn lives in 1888 England and pre-World War II Washington, DC. In the 1930s, when she curates a museum exhibit about Jack the Ripper, she discovers that her sister will become his last victim in 1888. Kathryn must race against time to save her, knowing it will cost her everything--including the only man she's ever loved.