Sara Howard opens a private detective agency in New York; Sara reunites with Dr. Kreizler and John Moore.
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; Kreizler suspects dark goings-on at the Lying-In Hospital.
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; Moore introduces Sara to a well-connected friend.
After a Lying-In Hospital employee is murdered, the team is hot on the heels of the killer; Sara enlists the help of Joanna to tail their prime suspect; the gang finds that not even Sara's office is out of the killer's reach.
Sara and Moore search for new information about their suspect; Kreizler faces ruin after a tragic incident at the Institute; Sara and the team must work with their adversary, former Commissioner Thomas Byrnes, to rescue another missing child.
Sara, Kreizler and Moore travel to Brooklyn in search of clues hidden in the killer's dark past; Thomas Byrnes plans to double-cross the team as the killer's behavior becomes more and more unhinged.
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; the team must overcome the wrath of the police and an underworld gang to save innocent lives.