Atwater and Burgess are given a new patrol car, but are challenged with keeping it brand new. A run in with a psychotic woman leads the Intelligence Unit to discover a drug smuggling operation which has put several girl’s lives in peril. Voight’s overprotective act with Lindsay leads her right where he doesn’t want as she also helps to keep Justin out of trouble. Meanwhile on stakeout, things get tense between Olinsky and Ruzek as Olinski tries to teach him the finer points of surveillance.

The bounty on Halstead’s head becomes a serious reality as an innocent bartender takes a bullet meant for him. Olinsky tries to reason with Bembenek to call off the hit. Voight and the team keep this investigation in-house to find the hired assassin. After a tense interaction at district, Platt and Nadia come to an understanding.

Bob Ruzek is the first to arrive on the scene of a double murder. Intelligence arrives to take over the investigation and tensions arise as Bob needs to hand over the case to his son and Voight. Lindsay's new gig has her planning a trip to Bolivia for an undercover investigation that could be for an extended amount of time. Burgess and Roman realize they need to put past events behind them so it doesn't jeopardize them going forward.

Antonio and his sister Gabriela go to the office of Elliot Gish, the man they believe started the fire that killed Shay. Intelligence, along with patrol officers Burgess and Roman, put pressure on Gish to confess. Lindsay approaches Voight about returning to Intelligence when she realizes that the task force isn’t what she thought it would be. Desk Sgt. Platt has everyone curious why she’s being overly cheery, friendly and nice.

The crossover starts on Chicago Fire S03E13 Three Bells (I).

A mass shooting at an athletic club is investigated; and Atwater, who's dealing with his new assignment, helps locate the suspected shooters. Platt and Halstead, meanwhile, check in with Lindsay to see how she's managing.

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

Lindsay and Halstead respond to a shots fired call and discover one survivor: a young girl. Antonio and Olinsky investigate a "self help" group. Platt makes the case to Crowley for why Burgess and Roman should remain partners.

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.

Severide is brought into the District for questioning after his car is found to have caused a deadly crash. As the investigation gets underway, the team works to uncover a group of car-jackers who may be the key to Severide's innocence.

The crossover starts on Chicago Fire S05E09 Some Make It, Some Don't (I).

After the body of young woman is found with multiple gunshot wounds, Intelligence uncovers details of her case that are similar to other deaths. They work to link all of these murders together to pin down the serial killer, and appease the families of the victims who have been looking for answers.

When a gang from El Salvador infiltrates Chicago, Intelligence works with a visiting detective to put an end to the crew's brutal tactics. Meanwhile, Antonio finds himself getting close to Salvadoran Detective Marcella Gomez and Voight learns that the body of his son's killer has been found.

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.

The crossover continues on Chicago Fire S06E013 Hiding Not Seeking (II).

After Voight 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 gets a tip that a grand jury has been summoned, putting Olinsky one step closer to standing trial for Bingham’s murder.

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.

Politics get in the way as the team tries to rescue a teenage girl kidnapped by a robbery crew. Voight and Platt try to exonerate Olinsky.

Voight and Ruzek lock horns over how to handle the aftermath of the Antonio situation. Meanwhile, a series of violent carjackings turns deadly, and Ruzek must rely on a C.I. he grew up with to help solve the case.

When Atwater goes undercover in a dangerous South Side drug syndicate, he learns there may be more to its kingpin than meets the eye. Halstead tries to join Atwater undercover, but finds himself at a disadvantage. Voight petitions the brass to show Ruzek leniency in his court case.

After a botched carjacking turns out to be something much bigger, Voight’s unit goes toe-to-toe with a smart drug kingpin who only works with women. New recruit Vanessa Rojas struggles with the transition from undercover to Intelligence.

The shocking murder of young boys affects Halstead. Crawford encourages Intelligence to use a new facial-recognition software to help identify a suspect, but the plan backfires.

Voight pulls Darius in after Crawford asks Intelligence to investigate a dangerous drug, but there is little trust in the relationship. When their plan to nail a dealer goes awry and another CI is murdered, the team must make a tough decision about Darius.

Atwater goes undercover to take down a gun-trafficking ring, but discovers an officer from his past is undercover in the same organization.

A cop is murdered, and suspicion falls on someone who has been holding a grudge against the officer. Intelligence works hard to solve the case, but Deputy Superintendent Samantha Miller is hesitant to defend him until she knows the whole story.

Ruzek's father, Bob, goes missing and the team races to find him before it's too late.

After a series of brutal home invasion robberies, Upton immerses herself in the case and finds herself caught between Voight and Halstead.

Ruzek reunites with an old colleague to take down a crime ring but when things don’t add up, Voight and Burgess do some investigating of their own.

With the FBI closing in on the Roy Walton investigation, Voight and Halstead strategize on a way out. After a city bus driver is shot by a passenger, the team investigates a possible abduction.

Voight and the team delve into a cold case in search of clues to solve a shocking new crime. With its focus on buried memories, the case sparks concern for Burgess and Ruzek about Makayla's mental healing.

To distract Intelligence from the investigation into his son, Chief O'Neal forces the team to handle a "dead fish" case. However, when that dead fish turns into a complicated heater case, Burgess is thrown back into difficult memories from her past.

Sean O'Neal surprises Upton with a call from prison, revealing sensitive information. Meanwhile, the team quickly mobilizes to stop a crime in progress before it's too late.

Voight takes the stand in a high-stakes murder trial against notorious drug kingpin Arturo Morales. When it becomes clear that Morales and his henchmen have compromised a juror, Voight and the team work furiously to ensure justice prevails.

Returning from furlough, Torres goes undercover in a tense and high-stakes drug trafficking case.

Atwater turns to an unlikely source of support when a string of jewelry store robberies shakes his confidence.

An ongoing case hits close to home for Voight as Intelligence teams up with an SVU detective to track down a prolific offender.

As the monthslong investigation into the serial killer reaches its close, Voight must outsmart the offender in a race against the clock. Upton must make a vital decision.

After tragedy strikes Intelligence, the unit must persevere during an adrenalized manhunt across the city.

Burgess is put to the test as she looks to make an advancement in her career.