Halstead’s past resurfaces when a former Army colleague is implicated in a deadly blast. As the FBI launches an investigation into Roy’s disappearance, Upton feels the pressure of the secret she and Voight are sharing.

Halstead takes a new recruit under his wing during an investigation. The dynamics are challenging, however, and questions arise over the recruit's complicated past.

A shocking murder pulls rookie officer Dante Torres into his own neighborhood. As Voight and Atwater help him navigate the case and manage tricky personal dynamics with wary neighbors, Torres realizes his life may be forever changed.

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

As the team investigates a convenience store robbery, the evidence leads them to an unusual pair of suspects, revealing a dark personal drama and another potential victim. Burgess slowly makes strides tackling her past trauma.

Atwater turns to an unlikely source of support when a string of jewelry store robberies shakes his confidence.