The story of Windy City's Police Department in Chicago.
Cast: Don Kress, Andre Bellos, Jason Beghe, Sophia Bush, Patrick John Flueger, America Olivo, Jon Seda, David Aron Damane, Zach Garcia, Laroyce Hawkins, Heidi Johanningmeier, Christopher Kahler, Kurt Naebig, Emily Peterson, Joe Reegan, Matthew Sherbach, Isaac White
The team investigates the stabbing of a father with two young daughters; they begin to suspect there is more to the story than meets the eye. The FBI investigation into Roy Walton's death intensifies.
As the team works to bring down a drug ring, Voight builds trust with a new informant. However, it soon becomes clear she has a plan of her own.
Ruzek reunites with an old colleague to take down a crime ring but when things don't add up, Voight and Burgess do some investigating of their own.
As the team works to solve a deadly shooting in Burnside, Atwater realizes he has a very personal connection to the case.
When Upton and Ruzek answer an emergency call to an abandoned house, their investigation leads them down a dark path. Upton feels the pressure of the secret she and Voight are sharing.
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.
Burgess fights for her life. Dep. Supt. Sam Miller is desperate to find her son's killer. Voight and Upton deal with the aftermath of their deadly decision. Ruzek struggles with the pressure of the situation.
When a P.D. informant is murdered, the team digs in to track down the perpetrator only to learn a shocking truth. Voight and Ruzek strategize to help Burgess.