The team investigates a Columbine-like threat at a private school. Atwater seeks out a mentor; Olinsky's marriage faces a crisis.

While working at a sobriety checkpoint, Burgess finds a duffel bag full of heroin in the truck of a respected college professor who claims to know nothing about how the drugs ended up there. At District, Roman expresses his desires to become a Field Training Office to Platt, and Mouse sets Halstead up with an off-duty security job working for the attractive owner of a medical marijuana clinic.

After receiving a complaint from a frustrated neighbor, Burgess and Officer Sorensen arrive to the house of baseball player Jake McCoy, and find the dead body of a 16-year-old girl, Maya Collins. There is conflict within the case as Intelligence learns that Olinsky and McCoy are friends, and McCoy admits that he was helping Maya and other girls try to escape the sex trade. Meanwhile, Burgess and Sorensen track down a thief who turns out to be a cop with a rocky past, and Lindsay gets a mysterious flower delivery that may be tied to her past.

After a female jogger is brutally murdered in the park, Rixton and Atwater arrive to see two suspects fleeing the scene. When the men make their way inside a church, the priest and parishioners gather outside to block law enforcement from entering. While investigating the case, Rixton gets caught in a lie with Voight.

After encouraging her sister to spend a night out with friends, Burgess wakes to find that Nicole never made it home. As the guilt begins to eat at Burgess, the team in Intelligence bands together to make finding Nicole their main priority.

A live video is streamed online showcasing a tortured man being beaten and burned alive. Upon further investigation, the victim's identity is traced back to that of a man who had been previously locked up for statutory rape. When another attack of a similar nature occurs, Intelligence finds a connection between the crimes, suspected pedophiles, and group named the Perv Hunters.

When a young Latina woman is brutally murdered, Intelligence suspects she may have been working as a drug mule. With Antonio leading the case, the team's investigation takes them into the grim world of meat processing, and the discovery that there may be a different motive behind her death.

The death of Judge Tommy Wells' daughter puts Intelligence on the track of a pill mill spreading into the suburbs of Chicago and the doctor enabling it. Meanwhile, Voight discovers who's been leaking information from the 21st.

When a basketball star is found murdered after an anti-police rally, Intelligence navigates a politically charged environment to track down the killer. To complicate matters further, Woods' daughter Brianna is tangled up in the case.

Halstead and Atwater go under cover to prevent military-grade weapons from hitting the street; Voight calls in a favor to clear Olinsky's name for Bingham's murder.

Tensions run high as Intelligence seeks justice for Olinsky after he's stabbed in prison; Antonio's loyalty is put to the test; Woods looks to take down Voight once and for all. Season Finale.

In an attempt to dig himself out of a hole and save someone close to him, Antonio crosses a line that puts the entire team at risk.

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.

A mayoral candidate is shot by an unidentified sniper, and Intelligence races to catch the shooter before he can take out his next target.