FBI Special Agent A. X. L. Pendergast always wants to protect his protegee Constance Greene from harm. But, against all odds, Constance has found a way to travel back in time. Heading to New York City in the late 1800s, Constance returns to the century of her birth to embark on a dangerous quest: stopping the era's most infamous serial killer, Dr. Enoch Leng, from bringing his nefarious plans to fruition.If Constance can stop Dr. Leng, she can finally prevent the events that led to the shocking deaths of her sister and brother... but can she survive herself, when up against one of the cleverest and most evil men of his age?Meanwhile, in present-day New York, Agent Pendergast is desperate to reunite with Constance before she gets stuck in the past forever... but can he find a way to reach before it's too late?