With Voight sidelined, Antonio and Ruzek clash as Intelligence races to solve a high-stakes case involving a series of overdose deaths caused by bad heroin.
Intelligence joins forces with Firehouse 51 after a devastating high-rise fire is ruled arson, and Halstead, who has a tragic connection to the fire, struggles to stay objective as he gets deeper into the investigation.
Intelligence's investigation into a string of robberies targeting vulnerable immigrants escalates when a teenage girl connected to a critic of the CPD is kidnapped by the robbers.
Burgess finds herself in a difficult situation when she responds to a call while a civilian is in her car for a ride-along that was requested by Brennan.
Intelligence's investigation of a nightclub owner suspected of cocaine distribution is complicated when Ruzek recognizes someone close to him while working undercover.
When the wife of an alderman is beaten to death, Voight finds himself under pressure from Brennan to close the case; Upton shares a dark episode from her past to elicit a confession.
Voight urges Halstead to remain impartial and follow the facts when the leader of a local mosque becomes the suspect in the bombing of an Army recruitment center.
The stakes become personal for Atwater during Intelligence's investigation of a drug dealer suspected of homicide.
As his dependency on prescription painkillers grows, Antonio crosses a line, endangering someone close to him and ultimately putting the entire team at risk.
Intelligence investigates a carjacking turned homicide; Ruzek makes a decision that puts his life and career at risk to protect those close to him.
Intelligence crosses with a mayoral candidate while investigating the fatal shooting of a well-known defense attorney; Antonio returns to work but questions his own judgment when an operation goes sideways.
Voight pursues a suspect against the police commissioner's orders; Halstead puts his career at risk when a case involving a recently released drug dealer turns personal.
When Atwater goes under cover to bring down the longtime head of a criminal enterprise, he 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.
When Cruz's undercover work reveals a lead in a case tracking multiple robberies, the situation escalates quickly, causing friction between Voight's Intelligence Unit and the Chicago Fire Department.
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.
A mayoral candidate is shot by an unidentified sniper, and Intelligence races to catch the shooter before he can take out his next target.
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; Voight takes a shot at Kelton to protect his team.