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.

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.

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 Senora Linares.

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.

After the horrific murder 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.

Sara and Moore return to the killer'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.

Sara, Kreizler and Moore travel to Brooklyn in search of clues. Byrnes plans to double-cross the team as the killer's behavior becomes 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 killer, and the team must overcome the wrath of the police and an underworld gang on the rampage.