After a brutal shooting, Burgess and Ruzek find themselves trapped aboard the busy "L" subway train. As they piece together scant evidence, the team is drawn into a dark family drama. Burgess' proximity to the shooting triggers harsh memories.

Voight takes the stand for ASA Chapman in a high-stakes murder trial against notorious drug kingpin Arturo Morales. When it becomes clear that Morales and his henchmen have compromised a juror, Voight and the team work furiously to ensure justice prevails.