Voight and Ruzek lock horns over how to handle the aftermath of the Antonio situation. Meanwhile, a series of violent carjackings turns deadly, and Ruzek must rely on a C.I. he grew up with to help solve the case.
An investigation into the death of a well known district attorney puts the Intelligence Division at odds with a mayoral candidate. Antonio returns to work but doesn't trust his own judgment when an operation goes sideways.
While chasing a heroin supplier, CPD crosses paths with a convicted criminal recently released on a technicality. Halstead's history with the man threatens the team's ability to put him back in prison.
Atwater goes undercover to bring down the longtime head of a criminal enterprise and becomes entangled in a situation that tests his allegiances as well as his conscience.
Upton and Burgess find themselves in a difficult situation when Intelligence tracks a cache of cop killer machine guns to a local gun show in Wisconsin.
Using information from Cruz, Intelligence chases down the robbery crew that's been using the lockbox key. Voight is under pressure to bring the crew to justice without tarnishing the reputation of a murdered firefighter.
Voight and the Intelligence Unit focus all their effort and resources into investigating the disappearance of an exotic dancer who served as a long-time criminal informant for their team.
With the threat of a gang war looming, Voight and Ray Price must organize a peace summit to end the bloodshed before more innocent people get hurt. Burgess evaluates her future with Blair.
Intelligence's investigation into the murder of Burgess' boyfriend threatens to reveal a dark side she was unaware of. The real motivation for his murder uncovers a much more unsettling truth.
A violent crew is hitting pharmaceutical delivery trucks and stealing drugs but their motivation is more complicated than just money. The case tests Upton and Ruzek's relationship.
Antonio struggles with his guilty conscience as he tries to take down a major drug dealer. In order to protect his team, Voight takes a big shot at Kelton.
When Kelton is found murdered, Voight's grudge against the mayor-elect puts him under suspicion; Upton and Halstead want to prove their sergeant's innocence, but the more evidence they gather, the closer they come to doing the opposite.
When Atwater goes undercover in a drug syndicate, he learns there may be more to its kingpin than meets the eye; Halstead tries to join Atwater undercover, but finds himself at a disadvantage.
After a botched carjacking turns out to be something much bigger, Voight's unit goes toe-to-toe with a smart drug kingpin who only works with women. New recruit Vanessa Rojas struggles with the transition from undercover to Intelligence.
After zeroing in on a suspect responsible for bioterrorism, the P.D. prepares to undertake their biggest manhunt yet. Upton is torn between helping track down the perp and providing emotional support to a scared young girl who needs her..
The shocking murder of young boys affects Halstead. Crawford encourages Intelligence to use a new facial recognition software to help identify a suspect, but the plan backfires.
Voight pulls Darius in after Crawford asks Intelligence to investigate a dangerous drug, but there is little trust in the relationship. When their plan to nail a dealer goes awry and another CI is murdered, the team must make a tough decision about Darius.
After injuring herself while pursuing a suspect, Burgess receives a shocking diagnosis. A homicide case turns into a missing persons case, with a sinister twist. Voight has to decide between justice and the letter of the law.