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.