While dealing with the police reform revolution, the Intelligence Unit looks into a case of a five-year-old girl who gets involved in a shooting. After he gets into a brawl with Voight over the case, Atwater is ambushed by a group of unknown persons and is left for dead.
As the son of a powerful ex-cop gets implicated in a murder, Moore puts pressure on Voight to bring him to trial as soon as possible. After patrol cops refuse to respond to his team's requests, Atwater's struggle against the blue wall escalates.
As Ruzek and Burgess come upon a female youngster while on patrol, they learn that all of her family members have been killed and that she's the only witness. Upton considers an FBI job opportunity.
When a Chicago cop is killed, the prime suspect turns out to be someone who was at loggerheads with him, but Voight is having trouble persuading the Deputy Superintendent to join the investigation.
While looking into a number of brutal carjackings, the Intelligence Unit discovers that the perpetrators are foster teens who belong to a teen prostitution ring. Burgess discovers, after apprehending one of them, that the youths did it for the sake of a better livelihood.
The Intelligence Unit cops, while on secret surveillance, stumble upon a man who is caught peddling heroin. To their shock, the man admits that he is working for a group of gangsters to find out who killed his son.
Ruzek enlists the assistance of his CI following an accident that involved the killing of a group of meth drug dealers, but things take an unexpected turn when Ruzek's CI jeopardizes the investigation.
Following a shooting, Ruzek and Atwater are assigned the task of apprehending a patrol cop, yet things take an unexpected turn when it becomes evident that someone intends to murder the cop, which results in a perilous situation.
After a local shop owner gets murdered, Miller urges Voight to send Officer Andre Cooper incognito to arrest the suspect, only for Cooper to develop a connection with him.
Officer "Disco" Bob Ruzek, Ruzek's father, is abducted by a gang, who are seeking to learn information about a confidential human source in return for his life, upon which the Intelligence Unit must take the bull by the horns to save him.
Upton is haunted by a series of traumatic childhood recollections when the Investigation Unit cops look into the kidnapping of a family that has been experiencing domestic violence and financial hardships.
The team is on the trail of a cunning serial rapist who has perpetrated a slew of killings with no evidence left behind. Voight strives to overcome his investigative instincts after Deputy Superintendent Miller argues that the CPD should follow the rules.
The team is tasked with tracking down the murderer of a young pregnant lady, which leads to something far worse than thought. Burgess mulls over who should be responsible for parenting her recently adopted daughter, Makayla, if anything bad befell her.
While the team is working on a case of violent home invasions, Upton begins to worry if her romance with Halstead is impacting her job as a cop. Meanwhile, Voight grows suspicious that Upton and Halstead are having an affair.
As Voight and his crew are on the trail of a vicious crime syndicate, things take an unexpected turn as they delve further into the investigation. Deputy Superintendent Miller calls her decisions into question.
The cops at the Intelligence Unit are trying to find Burgess who recently got abducted, but the situation escalates, leading to a brawl between Ruzek and Atwater. Meanwhile, Voight extends the limits of what is possible in his quest to locate her.