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.

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.

When a P.D. informant is murdered, the team digs in to track down the perpetrator only to learn a shocking truth. Voight and Ruzek strategize to help Burgess.

Officer Kim Burgess fights for her life as the team scrambles to find her kidnapper. Dep. Supt. Sam Miller is desperate to find her son's killer. Voight and Upton deal with the aftermath of their deadly decision. Ruzek struggles with the pressure of the situation.

Halstead’s past resurfaces when a former Army colleague is implicated in a deadly blast. As the FBI launches an investigation into Roy’s disappearance, Upton feels the pressure of the secret she and Voight are sharing.

When Upton and Ruzek answer an emergency call to an abandoned house, their investigation leads them down a dark path.

As the team works to solve a deadly shooting in Burnside, Atwater realizes he has a very personal connection to the case.

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.

As the team works to bring down a drug ring, Voight builds trust with a new informant. However, it soon becomes clear she has a plan of her own.

As the team investigates the stabbing of a father with two young daughters, they begin to suspect there is more to the story than meets the eye. The FBI investigation into Roy Walton’s death intensifies while Voight, Upton and Halstead feel the heat.

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.

The team searches for a missing child in what turns out to be a very complicated case. Burgess and Ruzek are in for a shock when someone from Makayla’s past comes forward.

Voight employs his new informant to help solve a tricky drug trafficking case. Atwater, who once again struggles to reconcile his personal and professional life, reaches a decision.

The team works together to identify the head of the brutal Los Temidos gang. Voight dives deeper into his informant Anna Avalos' past when her undercover role is threatened.

While out for a jog, Upton witnesses a horrible car crash and risks her own life to save the passengers. After learning more about the victims, the team must track down the man responsible for the brutal crash.

The team searches for a brutal killer with a signature modus operandi. Burgess and Ruzek double down in their fight to retain custody of Makayla.

The unit scrambles to search for one of their own who is in grave danger.

When a young man is shot outside the Cárabo Bakery, the team works to connect the shooting to bakery owner Javier Escano, who has been under surveillance. Despite the increasing danger, Voight helps informant Anna Avalos get even closer to their target.

Ruzek's search for the daughter of an old family friend leads the team into a serious drug investigation. Burgess and Ruzek struggle to move on from the emotional aftermath of Makayla's abduction.

Halstead takes a new recruit under his wing during an investigation. The dynamics are challenging, however, and questions arise over the recruit's complicated past.

After the murder of a wealthy Chicago man, Atwater and the team dig in to uncover the truth, suspecting there is more to the story than meets the eye.

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.

As the team closes in on drug kingpin Javier Escano, Voight is forced to lie to his undercover informant Anna to keep her on track. Their deteriorating trust threatens an increasingly tenuous operation.

After an explosion rocks the case, the team scrambles to finally take down Escano as everyone nears their breaking point.

Still reeling from the death of informant Anna, Voight faces a new threat as he tries to keep the neighborhood clean. New wrinkles develop in the Upton, Halstead and Voight dynamic. The team gets a new chief.

When a convicted murderer hijacks a prison van, the team scrambles to find him and the abducted prison guard before it's too late. Burgess questions Ruzek's motives in a case, creating tension between the two.

The team investigates a string of brutal pharmacy robberies, and Halstead connects with one of the victims about their Army careers. Upton suspects there is more to the story and confides in Voight.

A shocking murder pulls rookie officer Dante Torres into his own neighborhood. As Voight and Atwater help him navigate the case and manage tricky personal dynamics with wary neighbors, Torres realizes his life may be forever changed.

Upton's dogged pursuit of a missing teenage girl leads the team into a dark web of human trafficking. Chief O'Neal becomes involved with the unit's investigation when it becomes evident his son, Sean, has a connection to the missing girl.

Atwater’s reactions during a tense arrest are called into question. The team must dig in to uncover key evidence that could aid in the ongoing investigation and clear Atwater’s name.

When actionable evidence finally surfaces against Sean O'Neal, Upton and the team work relentlessly to build a case in secret. They discover Sean is more elusive and dangerous than anticipated.

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.

After a shocking discovery, the team begins closing in on Sean O’Neal with every shred of evidence they can find. Determined to keep his son out of prison, Chief O’Neal hires a lawyer.

A series of brutal home invasion robberies finds the team paired with Detective Borkowski, an old friend of Ruzek's, to work the case. Things get complicated for Torres when it becomes clear Borkowski has a vastly different policing style.

A shocking ambush at a funeral leads the team into a heated investigation to find the shooters. Much to Atwater's surprise, he must rely on someone from his past to help in the investigation, dredging up old memories and revealing new truths.

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 and the team help ASA Nina Chapman pursue a drug runner who dodged prison years ago after Chapman's informant mysteriously disappeared. The investigation takes a turn when Voight uncovers a damaging secret from Chapman's past.

After a brutal shooting, Burgess and Ruzek find themselves trapped aboard the busy "L" subway. As they piece together scant evidence, the team is drawn into a dark family drama.

When a family is poisoned in their home, the team discovers a connection to the Becks. Ruzek goes undercover to work for their business, and as he gets closer to Samantha, chilling information about her father, Richard, comes to light.

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.

As the team investigates a convenience store robbery, the evidence leads them to an unusual pair of suspects, revealing a dark personal drama and another potential victim. Burgess slowly makes strides tackling her past trauma.

A tragic crime leads the team closer to the Beck family and their deadly ideology. Ruzek makes progress infiltrating the Becks, earning Samantha and Richard's trust with a bold move.

Atwater's worlds collide when a shooting at the building he owns in Burnside leaves a child dead. Atwater must confront his relationship with his father, Lew, as the brutal case forces them together.

Upton is unwittingly drawn into a deadly betrayal and finds herself in a fight for her life. With minimal leads, Voight and the team scramble to find her before it's too late.

Torres finds himself in the midst of a murder case that hits close to home and threatens to expose his troubled past. As he struggles to reconcile his old life with his new one, Voight keeps a watchful eye.

As Richard Beck's timeline for a deadly attack moves up and Samantha panics, Ruzek and the team scramble to get ahead of unprecedented disaster.

A month after Voight's close brush with death, Intelligence is overwhelmed with cases as they catch a high-stakes drug bust.

Atwater struggles to find balance as he teams up with a forensic psychologist on an armed robbery case.

Torres is haunted by his previous transgressions as Cook takes on a tense undercover assignment.

An unexpected visitor causes disruption for Ruzek and Burgess amidst an emotional investigation involving an unidentified young girl.

A mounting street war threatens a community-center project that Atwater is trying to get off the ground.

Burgess' memory recall is put to the test following a deadly incident at her local diner.

Cook works with a confidential informant for the first time in a robbery-murder case with links to a star college athlete.

Forced to cease operations while under investigation by Internal Affairs, Intelligence goes off-book to bring down Reid once and for all. Ruzek and Burgess consider delaying their nuptials amid the uncertainty.