Bad heroin is causing overdoses in Chicago, and Intelligence is a man down with Voight suspended. Antonio takes charge, but Ruzek undermines his authority.

After discovering the true cause of the high-rise fire, Intelligence races to find the man responsible. And for Halstead, it’s personal.

The crossover starts on Chicago Fire S07E02 Going to War (I) and Chicago Med S04E02 When to Let Go (II).

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.

A ride along goes sideways, and Burgess is faced with a difficult choice: follow the advice of Voight, or a potential new ally.

While undercover, Ruzek discovers his father is working for a suspected drug dealer and is forced to ask the question: is his dad involved?

The wife of an alderman is beaten to death, and Voight is under pressure from First Deputy Superintendent Brennan to close the case. To elicit a confession, Upton tells a dark story about her childhood.

Intelligence suspects the leader of a local mosque is behind the bombing of an Army recruitment station. After a second explosion, Voight urges Halstead to follow the facts and not let his time in the service cloud his judgment.

While CPD tries to take down a drug kingpin, Atwater faces a tough choice between doing what’s required to solve the murder of a young dealer and what’s best for the community.

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.

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.

Intelligence crosses with a mayoral candidate while investigating the fatal shooting of a well-known defense attorney. Antonio returns to work but questions his own judgment when an operation goes sideways.

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.

Atwater goes undercover to bring down the longtime head of a criminal enterprise and becomes entangled in a situation that tests his allegiances as well as his conscience.

Upton and Burgess find themselves in a difficult situation when Intelligence tracks a cache of cop killer machine guns to a local gun show in Wisconsin.

Using information from Chicago Fire's Cruz, Intelligence chases down the robbery crew that’s been using the lockbox key. Voight is under pressure to bring the crew to justice without tarnishing the reputation of a murdered firefighter who might have been involved.

The crossover starts on Chicago Fire S07E15 What I Saw (I).

Voight and the Intelligence Unit focus all their effort and resources into investigating the disappearance of an exotic dancer who served as a long-time criminal informant for their team

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

With the threat of a gang war looming, Voight and Ray Price must organize a peace summit to end the bloodshed before more innocent people get hurt. Burgess evaluates her future with Blair.

Intelligence's investigation into the murder of Burgess' boyfriend threatens to reveal a dark side she was unaware of. The real motivation for his murder uncovers a much more unsettling truth.

A violent crew is hitting pharmaceutical delivery trucks and stealing drugs, but their motivation is more complicated than just money. The case tests Upton and Ruzek’s relationship.

Antonio struggles with his guilty conscience as he tries to take down a major drug dealer. In order to protect his team, Voight takes a big shot at Kelton.

With Kelton’s election all but assured, Voight and his team must go off book in a last-ditch effort to save Intelligence from getting axed.

When Kelton is found murdered, Voight's grudge against the mayor-elect puts him under suspicion. Upton and Halstead are eager to prove their sergeant's innocence, but the more evidence they gather, the closer they come to doing the opposite.

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.

After zeroing in on the suspect responsible for the bioterrorism that’s gripping Chicago, the PD prepares to undertake their biggest manhunt yet. Upton is torn between helping track down the perp and providing emotional support to the scared young girl that needs her. Voight fears his team is being sent on a wild goose chase.

The crossover starts on Chicago Fire S08E04 Infection (I) and Chicago Med S05E04 Infection, Part II (II).

A murder in a Bulgarian neighborhood results in a challenging investigation when locals won't talk to police. Ruzek has a clash with a patrol officer.

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.

After injuring herself while pursuing a suspect, Burgess receives a shocking diagnosis. A homicide case turns into a missing persons case, with a sinister twist. Voight has to decide between justice and the letter of the law.

Halstead's secret ongoing relationship with a woman connected to another case puts him in jeopardy.

As they await news of Halstead’s fate, the team tries to focus on work, turning their attention to an illegal arms dealer. Atwater discovers his brother, Jordan, is back in Chicago and could be tied to the case. Voight faces the tricky task of how to deal with Halstead’s shooter. Burgess finally makes her decision.

Ruzek and Burgess’s secret begins to have severe implications for their police work. A series of deadly acts of vandalism causes tensions to run high in the insular neighborhood of Canaryville. Atwater tries to reach out to his brother, but only pushes him further away.

Voight makes a deal with Darius Walker to help bring down a rogue group of dirty cops dealing drugs that were supposed to be destroyed. Upton clashes with Voight and enacts her own form of justice.

After receiving a distressing 911 call, Burgess enlists the team's help to track down a girl caught up in a sex-trafficking ring.

A homeless man's murder leads Intelligence to a criminal who has evaded capture for years. Rojas has a troubling experience with a young mentally ill man.

Intelligence searches for the dealer who caused multiple overdoses and is connected to Roman's missing sister. The case becomes a homicide investigation when they find the dealer's dead body.

The crossover starts on Chicago Fire S08E15 Off the Grid (I).

An armed robbery case quickly turns into a homicide investigation. When one suspect’s background suggests domestic violence, Upton is forced to reckon with her childhood. Voight and Halstead butt heads over Halstead’s righteous instinct.

Voight enlists the help of a reformed gang member to get a key witness' testimony in a murder case. More lives are put on the line as a gang war brews.

Intelligence does everything they can to build a case against the elusive leader of a drug ring, but things get complicated when Rojas realizes someone she cares about might be involved.

The clock is on after Ruzek witnesses a woman's kidnapping and the team races to put the pieces together. Burgess tries to connect with Ruzek outside of work but he mysteriously distances himself from her.

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

The team responds to the shooting of a 5-year-old girl and must work the case while facing new obstacles that come from the heightened attention on police reform. Atwater is targeted by a group of officers who want to hurt him for standing against the blue wall. Voight questions whether he's cut out for a new form of policing as he manages oversight from the CPD's deputy superintendent.

When the son of an influential former officer is implicated in a murder, Moore pressures Voight to charge him quickly. The stakes are raised in Atwater's fight against the blue wall after patrol officers stop responding to his team's calls.

Ruzek and Burgess discover a child walking alone in the middle of the street, and when they take her home, they discover that her entire family has been murdered. Upton is approached with a job offer from the FBI.

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.

The team investigates a rash of car jackings and finds the truth is more complicated than they realize. Burgess makes a discovery about a previous case that will change her life forever.

Halstead and Ruzek try to infiltrate a crime ring and encounter a complicated situation. The team recruits an unlikely ally to help solve a murder.

After a series of deadly ambushes, the team goes undercover to bring down a dangerous new drug dealer who is determined to push out the competition. Ruzek's informant proves to be a loose cannon that could upset the whole operation.

Ruzek and Atwater are tasked with making an arrest after a high-profile shooting. The situation becomes complicated when it's clear someone doesn't want them to make it back to the station.

When a local business owner is gunned down in his shop, it becomes personal for Atwater, who patrolled the neighborhood as a young cop. Dep. Supt. Samantha Miller comes to Voight with a special request about Andre Cooper.

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

A wellness check on a family reveals signs of foul play and Upton is determined to find the parents and young daughter. As Hailey delves further into the troubled family dynamics, she finds herself reflecting on her own childhood trauma.

The team pursues a crafty serial rapist. Sergeant Voight finds himself resisting some old, familiar tendencies in his quest for justice.

The shocking murder of a young pregnant woman leads the team on a desperate hunt for the killer, revealing something even darker than expected. Burgess has to make a tough decision about Makayla.

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

Voight and the team pursue a ruthless crime ring whose business has hit close to home. As they dig deeper, the extent of the danger becomes more apparent. Deputy Superintendent Samantha Miller second-guesses her decisions.

Voight and the team muster all their expertise to bring down a deadly crime ring. Burgess finds herself in a dangerous situation.