Chloe Jo Rountree

Following the subway tunnel collapse, Ruzek and Kidd treat injured passengers and track down the missing offender. Archer and Frost perform a life-saving amputation. Lenox feels the weight of the CPD's hopes as she fights to save one of their own.

With the suspects still at large and conditions worsening underground, first responders race against the clock to reach the trapped victims, while the investigation into the assailants comes into focus.