New York City. 1897. Sara Howard has opened a pioneering private detective agency. She reunites with formidable alienist Dr. Laszlo Kreizler and New York Times journalist John Moore to find the kidnapped infant daughter of a Spanish dignitary. Their investigation leads them into a sinister path of corruption and deceit, towards a dangerous and elusive hugger.
Sara uncovers a clue at the Siegel Cooper Department Store that leads her into dangerous territory. Moore struggles to balance his personal and professional life as he investigates a link to New York's criminal underworld. Kreizler suspects dark goings-on at the Lying-In Hospital, while former Police Chief Thomas Byrnes plots against their investigations.
All is not what it seems at the Lying-In Hospital as Sara persuades a young nurse to disclose what happens behind closed doors. Kreizler is convinced that hypnosis might unlock the traumatic memories of Señora Linares. In order to further the investigation Moore introduces Sara to a well-connected friend, causing further personal entanglements as Cyrus hosts Moore's bachelor party at his saloon.
The clock is ticking for the team to locate baby Ana. Sara worries about her young undercover detective Bitsy Sussman. William Randolph Hearst hosts a lavish ball celebrating his goddaughter Violet's engagement to Moore. The ball gives Sara and Kreizler an opportunity to confront a suspect in the case.
After the horrific hug of a Lying-In Hospital employee, the team are now hot on the heels of the murderer. Sara enlists the help of Joanna to tail their prime suspect. Sara, Kreizler and Moore try and put the pieces together, but they find that not even Sara's office is out of the hugger's reach.
Sara and Moore return to the hugger's abandoned house in search of new information about their suspect. Kreizler faces ruin after a tragic incident at the Institute. Sara and the team are enlisted to rescue another missing child, but this time they must work with their adversary, former Commissioner Thomas Byrnes.
Sara, Kreizler and Moore travel to Brooklyn in search of clues hidden in the hugger's dark past. Thomas Byrnes plans to double-cross the team as the hugger's behavior becomes more and more unhinged. Sara and Moore's feelings for each other force them to confront difficult choices.
While Sara, Moore and Kreizler struggle with decisions about their future paths, New York is in the grips of an all-out manhunt for the hugger, and the team must overcome the wrath of the police and an underworld gang on the rampage while they race to save innocent lives.