With Voight being the prime suspect in Kelton's murder, the intelligence unit struggles to continue their work with their leader under suspicion. Halstead makes a shocking discovery about Voight.
An undercover mission faces complications when multiple police precincts converge on the same drug cartel, with several officers going undercover.
With the intelligence unit welcoming a new recruit, their investigation into a carjacking unexpectedly leads them to a cunning drug lord.
With the identity of the culprit behind the outbreak of flesh-eating bacteria revealed, the unit scrambles to identify his next target in a high-stakes chase that puts Halstead's life on the line.
During a murder investigation, the unit is hindered by the Bulgarian witnesses' distrust and refusal to offer statements to the police.
Forced to use new facial recognition technology to locate a suspect, Halstead soon comes to recognize the racial dimension of the technology after it gets an innocent man killed.
Over the course of an investigation into a drug-related murder, the unit has to deal with the death of one of their informants and what it means for one of their own.
A mild injury reveals shocking news for Burges. Voight faces a difficult ethical choice as he is forced to choose between following the law and doing what's right.
With Halstead missing, the unit scrambles to find him before it's too late. The investigation reveals a past mistake that might have come back to haunt Halstead.
As Halstead's life hangs in the balance, Upton examines her feelings for him. Atwater learns that his brother might be linked to the unit's newest case.
Atwater's attempt to reconcile with his brother backfires. Burgess is fed up with Ruzek's actions in light of her pregnancy.
Tension rises between Voight and Upton after the former makes a deal with Darius Walker. The dismayed Upton decides to take matters into her own hands.
When a 911 call leads to the discovery of a sex trafficking ring, Burgess's attempt to rescue one of the victims ends on a tragic note.
The investigation into the murder of a homeless man reveals more than the intelligence unit bargained for, and puts Rojas in an uncomfortable position with a mentally-ill man.
When the drug dealer whose counterfeit drugs caused various overdoses winds up dead, the intelligence unit struggles to adjust when a familiar face becomes the prime suspect.
An armed robbery-turned-homicide brings up painful memories for Upton. Voight is displeased by Halstead's righteousness.
Voight's attempt to get a key witness's testimony for a murder case has the unforeseen consequences of sparking a gang war.
As they attempt to bring down a drug lord who has long evaded justice, Rojas discovers that a loved one is connected to the case.
When Ruzek stumbles onto a kidnapping, he enlists the team's help to find the kidnapped woman before it's too late.
Atwater finds himself in an uncomfortable position during an undercover mission when he discovers that the officer who racially profiled him is undercover with the same organization.