The story of Windy City's Police Department in Chicago.
Cast: Don Kress, Andre Bellos, Jason Beghe, Sophia Bush, Patrick John Flueger, America Olivo, Jon Seda, David Aron Damane, Zach Garcia, Laroyce Hawkins, Heidi Johanningmeier, Christopher Kahler, Kurt Naebig, Emily Peterson, Joe Reegan, Matthew Sherbach, Isaac White
Lindsay's mother is a suspect in the murder of her boyfriend; and the case opens up when a group of high-school students OD, and the drugs in question relate back to the situation with Bunny. Lindsay also finds herself up against the review board dealing with consequences of her actions.
Intelligence tracks down a group of vigilantes torturing and killing pedophiles. Meanwhile, Lindsay runs into a few bumps in the road both personally and professionally.
When the team is called to an in-progress bank robbery, they come across a Robbery-Homicide detective trying to take over the crime scene; and, as the robberies continue, Lindsay makes a decision that unveils a surprising suspect behind the mask.
While investigating the murder of a teenage boy, Voight finds a connection with the murder weapon linking it to a case that he worked on 17 years ago. While the victim's father, a prominent defense attorney, tries to get the case taken over by Area Central Homicide, Voight digs back into the old case under the watchful eye of his former partner, Lt. Denny Woods.
Burgess's sister becomes a sexual assault victim after she's encouraged to spend a night out with friends.
Intelligence investigates one of Chicago's wealthiest families when "Night Crawler" Bobby Trent is murdered.
A hiker leads intelligence to a woman being held hostage in the woods outside Chicago.
Intelligence works to find the arsonist behind a warehouse fire that left Olinsky's daughter fighting for her life.
Intelligence re-opens a case when a grieving father seeks to avenge his daughter's murder.
When a burnt body is found in a torched house along with an injured boy, Intelligence works to find the cause.
Halstead goes undercover as a guard at a treatment center for troubled girls after one of its patients is found dead in an abandoned building; and Platt feels guilty because the victim was previously brought into the District, but she doesn't recall her.
The investigation of a jogger's murder in the park is blocked by a church offering sanctuary to the prime suspects.
When a mutilated sex offender is found dead, it is unclear if he was the victim of a hate crime, sexual assault or self-mutilation. As Intelligence questions those related to the case, they find themselves up against a private "special police" force who may be covering up illegal activities. Meanwhile, Halstead runs Jimmy's DNA to confirm that he is actually Lindsay's father.
When the body of a young woman is found, the Chicago police realize there's a serial killer at large after comparing her case with others.
Kelly Severide of Firehouse 51 is brought to the District for questioning when his car is found to have caused a deadly crash, so the team tracks down a group of carjackers that may prove Severide's innocence.
A highly trained killer declares war on the Chicago police department.
The team investigates the death of a witness in a rape-and-murder case in the first half of this combined episode, which also finds Stone offering Antonio a job in the state attorney's office. In the second half, the team searches for a cop killer; and Lindsay confronts Antonio about his new job.
Burgess and Sorensen discover a dead teen girl at the home of a baseball player who's friends with Olinsky; Burgess and Sorensen hunt a thief who turns out to be a cop with a rocky past; and Lindsay receives flowers.
Intelligence tracks down the people who have been dealing a drug that's been linked to several overdoses throughout Chicago.
A car plows through a crowd outside of a concert venue and is followed by gunfire, sparking fears that it may be terror-related. In other events, Burgess spots Atwater's brother where he shouldn't be; and the team works to bring peace to the community before more blood is shed.
Intelligence tracks down the people who've been dealing a drug that's causing multiple overdoses in the city.
Intelligence searches for the fiance of a man found badly beaten in the most dangerous neighborhood of District 21.
Intelligence investigates a murder-arson case as Voight and Lindsay continue to deal with the aftermath of Justin's death.