In the Trenches (2)

This is the second part of a major crossover with "Chicago Fire," "Chicago Med," and "Chicago P.D.":
Chicago Fire – S13E11 – In the Trenches (1)
Chicago Med – S10E11 – In the Trenches (2)
Chicago P.D. – S12E11 – In the Trenches (3)
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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.