Still reeling from the death of informant Anna, Voight faces a new threat as he tries to keep the neighborhood clean. New wrinkles develop in the Upton, Halstead and Voight dynamic. The team gets a new chief.
When a convicted murderer hijacks a prison van, the team scrambles to find him and the abducted prison guard before it's too late. Burgess questions Ruzek's motives in a case, creating tension between the two.
The team investigates a string of brutal pharmacy robberies and Halsted connects with one of the victims about their Army careers. Upton suspects there is more to the story and confides in Voight.
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.
Upton's dogged pursuit of a missing teenage girl leads the team into a dark web of human trafficking. Chief O'Neal becomes involved with the unit's investigation when it becomes evident his son, Sean, has a connection to the missing girl.
Atwater's reactions during a tense arrest are called into question. The team must dig in to uncover key evidence that could aid in the ongoing investigation and clear Atwater's name.
When actionable evidence finally surfaces against Sean O'Neal, Upton and the team work relentlessly to build a case in secret. They discover Sean is more elusive and dangerous than anticipated.
In an attempt to distract Intelligence from the investigation into his son, Chief O'Neal forces Voight and the team to handle a "dead fish case." However, when that dead fish turns into a complicated heater case, Burgess is thrown back into difficult memories from her past.
After a shocking discovery, the team begins closing in on Sean O'Neal with every shred of evidence they can find. Determined to keep his son out of prison, Chief O'Neal hires a lawyer.
A series of brutal home invasion robberies finds the team paired with Det. Borkowski, an old friend of Ruzek's, to work the case. Things get complicated for Torres when it becomes clear Borkowski has a vastly different policing style.
A shocking ambush at a funeral leads the team into a heated investigation to find the shooters. Much to Atwater's surprise, he must rely on someone from his past to help in the investigation, dredging up old memories and revealing new truths.
Sean O'Neal surprises Det. Upton with a call from prison, revealing sensitive information. While Upton grapples with how to keep O'Neal at a distance, the team quickly mobilizes to stop a crime in progress before it's too late.
Voight and the team help Assistant State's Attorney Nina Chapman pursue a drug runner who dodged prison years ago after Chapman's informant mysteriously disappeared. The investigation takes a turn when Voight uncovers a damaging secret from Chapman's past, threatening the investigation and Chapman's career.
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.
When a family is poisoned in their home, the team discovers a connection to the Becks. Ruzek goes undercover to work for their business and as he gets closer to Samantha, chilling information about her father, Richard, comes to light.
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.
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.
A tragic crime leads the team closer to the Beck family and their deadly ideology. Ruzek makes progress infiltrating the Becks, earning Samantha and Richard's trust with a bold move.
Atwater's worlds collide when there's a shooting at the building he owns in Burnside, which leaves a child dead. Atwater must confront his relationship with his father, Lew, as the brutal case forces them together.
Upton is unwittingly drawn into a deadly betrayal and finds herself in a fight for her life. With minimal leads, Voight and the team scramble to find her before it's too late.
Torres finds himself in the midst of a murder case that hits close to home and threatens to expose his troubled past. As he struggles to reconcile his old life with his new one, Voight keeps a watchful eye.
As Richard Beck's timeline for a deadly attack moves up and Samantha panics, Ruzek and the team scramble to get ahead of unprecedented disaster.
