The team searches for a missing child in what turns out to be a very complicated case. Burgess and Ruzek are in for a shock when someone from Makayla's past comes forward.
Voight employs his new informant to help solve a tricky drug trafficking case. Atwater, who once again struggles to reconcile his personal and professional life, reaches a decision.
The team works together to identify the head of the brutal Los Temidos gang. Voight dives deeper into his informant Anna Avalos' past when her undercover role is threatened.
While out for a jog, Upton witnesses a horrible car crash and risks her own life to save the passengers. After learning more about the victims, the team must track down the man responsible for the brutal crash.
When a young man is shot outside the Cárabo Bakery, the team works to connect the shooting to bakery owner Javier Escano, who has been under surveillance. Despite the danger, Voight helps informant Anna Avalos get closer to their target.
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.
Voight and the Team delve into a cold case in search of clues to solve a shocking new crime. With its focus on buried memories, the case sparks concern for Burgess and Ruzek about Makayla's mental healing.
As the team closes in on drug kingpin Javier Escano, Voight is forced to lie to his undercover informant Anna to keep her on track. Their deteriorating trust threatens an increasingly tenuous operation.
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. Voight and Atwater help him navigate the case and manage tricky personal dynamics with his wary neighbors. Torres realizes his life may change forever.
Upton's dogged pursuit of a missing teenage girl leads the team into a dark web of human trafficking. Chief O'Neil becomes involved with the unit's investigation when it becomes evident his son, Sean, has a connection to the missing girl.
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.
Chief O'Neal diverts Voight's team to a trivial "dead fish" case, hoping to distract from his son's investigation. The fish case grows complicated, triggering difficult memories for Burgess.
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.