After Voight (Jason Beghe) witnesses the kidnapping of a young woman with a mysterious connection to his past, Intelligence works to find a connection between her kidnapping and several bank robberies. Ruzek (Patrick John Flueger) gets a tip that a grand jury has been summoned, putting Olinsky (Elias Koteas) one step closer to standing trial for Bingham’s murder.
Halstead (Jesse Lee Soffer) and Atwater (LaRoyce Hawkins) go undercover to prevent military-grade weapons from hitting the street. Meanwhile, Voight (Jason Beghe) calls in a favor as a last-ditch effort to clear Olinsky’s (Elias Koteas) name for Bingham’s murder.
Upton (Tracy Spiridakos) brings back an old undercover identity to help take down a meth ring spearheaded by a former criminal contact. And with pressure from Woods (guest star Mykelti Williamson) mounting, Voight (Jason Beghe) calls in a favor for Olinksy (Elias Koteas).
A string of stash house robberies lead back to an unlikely individual. Voight (Jason Beghe) confronts a key witness in the Bingham investigation.
Intelligence investigates a string of bombings targeting members of the media. Racing against a ticking clock, the team enlists Firehouse 51 to help examine the devices and prevent the next attack.
When a prominent Alderman known for his urban revitalization efforts is killed, Intelligence looks into the corruption haunting his neighborhood. Meanwhile Olinsky (Elias Koteas) feels pressure after receiving an ultimatum from Woods (guest star Mykelti Williamson).
Antonio (Jon Seda) finds himself getting close to the Salvadoran Detective, Marcella Gomez (guest star Sofia Lama), only to learn she has a hidden motive for being in Chicago. Meanwhile, Voight (Jason Beghe) learns that the body of his son's killer has been found.
Intelligence tracks down a vigilante attacking rapists. The investigation hits home for Burgess (Marina Squerciati), who begins to question if the men who raped her sister truly paid for their actions.
While trying to find the pimp, Intelligence stumbles on the women's shelter where he's scouting out girls. And Burgess (Marina Squerciati) moves the case forward with a series of confidential tips, but risks putting her informant in harm's way.
When Atwater (LaRoyce Hawkins) disappears at the house of a convicted felon, the evidence doesn't look promising - with his belongings and his blood left behind. Intelligence rallies to rescue him before it's too late. And Atwater struggles for survival faced with not only his captor but also a difficult connection to his past.
The death of Judge Tommy Wells' (guest star John Pankow) daughter puts Intelligence on the track of a pill mill spreading into the suburbs of Chicago and the doctor enabling it. Meanwhile, Voight (Jason Beghe) discovers who's been leaking information from the 21st.
Halstead's (Jesse Lee Soffer) partying with Camila (guest star Anabelle Acosta) unintentionally puts him in the middle of a drug-related homicide. He's forced to choose between loyalty to his unit and his girl. Meanwhile, Voight (Jason Beghe) finally discovers the mole in his unit.
In the wake of several gang-related child abductions, Intelligence must race against time to find a kidnapped boy. Owing to their swiftness and military precision, the team scours the VA records and tracks the suspects to a former Army Ranger. With his previous experience as a Ranger, Halstead (Jesse Lee Soffer) convinces Voight (Jason Beghe) to send him undercover to try and get information from inside.
One of Voight's (Jason Beghe) friends, Congressman Scott Graynor (guest star Scott Bryce) is found passed out in his hotel room with a dead Ukranian girl. When Intelligence discovers the murder is connected to a sting and Burgess' (Marina Squerciati) boyfriend (guest star Zach Appelman) is working with the Feds, Burgess must choose between compromising her case or her boyfriend's case.
When Intelligence busts a meth lab run by gang leader Marshall Carter (guest star Aaron Roman Weiner), they uncover a re-homing scam in which children adopted from foreign countries are abandoned, then sold online. Meanwhile, Atwater (LaRoyce Hawkins) struggles with the difficult decision about whether to move his siblings Jordan (guest star Kylen Davis) and Vinessa (guest star Bobbi MacKenzie) to a safer environment outside of Chicago.
A picture perfect family is shot dead in their home and the team goes in search of a drug dealer with a likely connection. Voight (Jason Beghe) asks for the help of Vice Sergeant Sean McGrady (guest star Wil Traval) who has an old beef with Upton (Tracy Spiridakos). When McGrady turns up dead during the investigation, the case takes an unlikely turn.
When a young Latina woman is brutally murdered, Intelligence suspects she may have been working as a drug mule. With Antonio (Jon Seda) 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.
While investigating a drug-related homicide, Intelligence is stonewalled by the 'no-snitch' culture of the neighborhood. And Atwater (LaRoyce Hawkins) discovers a personal connection to the case. Meanwhile, the police's own code of silence is put to the test when Upton (Tracy Spiridakos) is asked about Ruzek's (Patrick John Flueger) rough altercation with a suspect.
When Lindsay (Sophia Bush) receives a panicked call from her mother Bunny (guest star Markie Post) whose boyfriend had just been shot, Lindsay must figure out the best way to approach the situation, as her mother is now a murder suspect. The case opens up when a group of high school students OD, and the drugs in question relate back to the situation with Bunny. In addition to her mother's issues, Lindsay finds herself up against the review board dealing with consequences of her actions.
After a van explodes during a Chicago street festival, a Muslim patrol officer Frank Toma (guest star Ben Youcef) goes missing and evidence quickly piles up pointing to his involvement. Burgess (Marina Squerciati) - who helped train Toma - is desperate to prove his innocence, even if that means going against her superiors.
When the team is called to an in-progress bank robbery, they come across Detective Hailey Upton (guest star Tracy Spiridakos) trying to take over the crime scene with her Robbery-Homicide unit - butting heads with Voight (Jason Beghe) in the process. As the robberies continue to be executed around the city, Lindsay (Sophia Bush) is forced to make a decision in the heat of the moment, revealing a surprising suspect behind the mask. While working on the case at the district, Upton is shocked to come across Platt (Amy Morton), who has a special connection to her past.
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. Meanwhile, Lindsay (Sophia Bush) runs into a few bumps in the road - both personally and professionally.