A suicide note is delivered to a surprised Dawson and Lt. Severide digs deeper into Bloom’s dark past. Elsewhere, Chief Boden learns shocking news, and with the help of Shay, Lt. Casey goes on the search for a life-changing item.

An ice storm hits, forcing a citywide lockdown. Mills and Brett are left stranded in the elements while searching for a teen, and the firehouse members babysit a newborn. Elsewhere, Severide receives a job offer, and Chief Boden clashes with his father over his treatment.

Severide lobbies Chief Boden for a favor for Scott Rice, an old friend needing a second chance with the CFD, but Casey and Otis have their doubts. Elsewhere, Mills works to regain his active squad status while Brett and Dawson decide they need a big night out.

The squad members come together to support one of their own. Herrmann tries to figure out how to reopen Molly's after it gets shut down. Severide digs deep into the arson investigation.

Herrmann fights for his life after being stabbed; Cruz hits the streets to find Freddie. Mouch proposes to Trudy.

The crossover continues on Chicago Med S01E05 Malignant (II) and Chicago P.D. S03E10 Now I'm God (III).

Freddie's father begs Herrmann to forgive his son's assault. Casey discovers that a makeshift shelter housing people displaced by the tornado may close. Casey attends a fund-raiser at the request of an alderman. Dawson and Brett experience repercussions after telling Boden about Chili's erratic behavior.

Casey reconsiders his run for alderman after he's targeted by a propaganda campaign. The squad responds when a man is trapped inside of a burning car. Trudy's nerdy brother plans Mouch's bachelor party. Jimmy and Brett investigate a kidnapping on their own.

Casey and Dawson find themselves in the midst a potential political mess. Stella has to make a big decision about her ex-beau. The squad responds to an auto accident. Severide befriends a socialite. Brett and Mouch set aside their writing differences for the greater good.

Lt. Casey is unable to rescue a woman who becomes trapped inside her burning greystone, prompting him and Lt. Severide to butt heads over the husband's role in the tragedy. Herrmann is on a mission to catch a mystery tagger that keeps targeting their firehouse and Boden gets a surprise visitor. Meanwhile, Dawson and Brett respond to a 16-year-old boy who was injured during a romantic homecoming proposal.

When truck and squad are summoned to the scene of a dangerous accident, Chief Boden makes a split-second decision that overrides Chief Anderson, the incident commander whose house was the first to respond to the call. Feeling his authority was undercut and his reputation damaged, Anderson uses his power to make things miserable for Boden and all of House 51 feels the repercussions.

When a turf war escalates, members of truck and squad find themselves caught in the middle as unsuspecting hostages when a group of armed gang members take cover and assume control over Firehouse 51.

When the squad's rig breaks down in the field, Casey reunites with his old friend and colleague Jason Kannell from Squad 6. Dawson and Brett serve their time in retraining. Severide tries to remedy what is going on with Anna and finds support from unlikely sources. As Connie returns from her family engagement, the crew lays bets on how long her temporary replacement Marcy will last.

With most of the squad still trapped inside the burning warehouse fire, Chief Boden makes a risky last-minute decision in an effort to save his men. Dawson continues to deal with her father, who has new plans for himself. Brett's childhood friend Hope visits the Windy City and strikes the attention of someone within the firehouse, while Kidd goes head-to-head with her landlord. Meanwhile, a fire at a high school hits close to home for Boden.

After heroically saving a mother and newborn baby from a rooftop fire, Kidd receives surprising news when she discovers she is being transferred out of the firehouse. Severide and Casey believe something is off about the turn of events, prompting them to investigate the situation. Otis and Herrmann discuss the possibilities of taking over a rundown bar and Dawson's frustration with her father, Ramon, reaches a boiling point.

After responding to a time-sensitive rescue, Casey and Severide don't see eye to eye on the best course of action. Herrmann struggles to entertain his daughter on "bring your child to work day." Brett is joined by a surprise guest during a spa getaway, courtesy of Dawson, while Kidd's social life gets a boost.

In response to a call involving a residential fire, Otis and Kidd's lives are suddenly put in jeopardy when gunfire goes off inside the house. Dawson comforts Brett during an especially trying time. Meanwhile, Casey begins to notice that romance might be going on within the firehouse.

After saving a girl from a car accident, Chief Boden and Lt. Severide are taken aback when they receive a surprise package. Brett struggles to keep quiet about Cruz reacquainting with his now-married high school sweetheart and Otis tackles his next challenge. A crisis brings Bria back into Dawson's life.

Boden's chances for a promotion are met with potential complications. Dawson and Casey don't see eye to eye on an important decision, while Kidd finds herself struggling to find time with Severide. Brett and Dawson respond to a tough call that quickly turns dangerous.

Firehouse 51 is faced with a daunting challenge when an out-of-control blaze consumes a 15-story apartment complex, trapping victims on the top floors. Complicating the rapidly escalating situation, members soon discover that someone close to home may be one of the trapped victims.

The crossover continues on Chicago Med S04E02 When to Let Go (II) and Chicago P.D. S06E02 Endings (III).

Stakes are high when a massive car pile-up on the freeway impacts someone dear to the firehouse family. Brett and Foster encounter a harrowing call while Kidd and Severide find their relationship being tested.

A spate of robberies comes to light after a firehouse lockbox key goes missing; Sergeant Hank Voight suspects a firefighter may be involved, and with Boden's support, he recruits Cruz to go undercover to help sniff out any suspicious activity.

The crossover continues on Chicago P.D. S06E15 Good Men (II).

A horrible storm wreaks havoc on Chicago and impacts Firehouse 51 when the power goes off. A little boy mysteriously shows up at the station and everyone works together to uncover who he belongs to. Foster and Kidd argue about Severide.

Severide and Kidd continue to investigate Benny’s old arson case, unexpected news leads Brett to ponder a big decision and all hell breaks loose.

The mattress factory fire spirals out of control. Truck and squad lay it on the line in hopes of getting the trapped victims out alive.

A rare but deadly bacteria takes its toll on numerous victims around the city, leaving Chicago’s finest first responders to work together alongside the CDC to resolve the dangerous situation. Following a fire at a local university that ties into the outbreak, Severide has suspicions that something bigger is happening.

The crossover continues on Chicago Med S05E04 Infection, Part II (II) and Chicago P.D. S07S04 Infection, Part III (III).

An unexpected visit throws Casey for a loop. Severide sets out to exonerate a wrongly convicted arsonist. Kidd pays the price for burning the candle at both ends. Cruz goes on a mission to fix one of Otis’s old toys.

A series of false alarms at a private school hinders the firehouse's ability to respond to legitimate emergency calls. Kidd asks for ideas to surprise Severide on his birthday. Cruz and Brett rent out their extra room, but the new tenant is more than they bargained for.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but begins to suspect there’s more to the story than his old friend is telling him. Casey tries to be there for Brett as she considers her birth mother’s offer to meet.

The crossover continues on Chicago P.D. S07E15 Burden of Truth (II).

Firehouse 51 welcomes a new member to the team, whose presence could provide some complications. Brett's leadership shines during a scary call. Boden sees great potential in Kidd and proposes an idea that could have lasting repercussions.

Brett and Mackey find their lives in peril. Casey and Brett tread in unfamiliar territory. Severide chases a memory while Kidd adeptly solves a firehouse problem. Ritter puts himself in harms way during a harrowing call.

When Firehouse 51 is called to the scene of a dangerous blaze inside a 10-story storage unit, Herrmann and Cruz find themselves trapped inside a freight elevator with all communications cut off.

Mouch, Gallo, Ritter and Mackey report for training. A nasty blow to the head brings Casey unimaginable pain.

A mysterious caller who is in danger relies on Kidd to help save her and her brother. The firehouse helps Cruz get ready for fatherhood.

Severide and Casey try to find the best fit for Kidd. Ritter, Gallo and Violet help plan an event for Mouch.

Firehouse 51 deals with the aftermath of the capsized boat rescue. Gallo, Ritter and Violet discuss plans for a side gig.

Casey makes a life-altering decision. Gallo, Ritter and Violet agree to an interview and photo shoot. Brett and Mouch launch the paramedicine program. Cruz comes closer to fatherhood.

Gallo clashes with the new lieutenant temporarily filling in for Casey. Severide closes in on a dangerous and deadly arsonist.

Gallo, Violet and Ritter debut their microbrewery business at Winterfest. Brett prepares to present her paramedicine program to an oversight panel. Firehouse 51 gets in the holiday spirit.

Severide and Kidd work with CPD regarding a suspicious car wreck. Hawkins and Violet's relationship is in jeopardy. Chloe and Cruz adjust to a new family dynamic.

The big wedding day arrives and Firehouse 51 welcomes Casey back to celebrate the joyous occasion. Emma's plans to replace Violet come to a shocking end.

Kidd and Severide's honeymoon is interrupted by a dangerous person from their past. Kidd's former academy classmate joins Firehouse 51. Brett and Violet reflect on their relationships.

Firehouse 51 hosts a Halloween open house. Kidd and Severide help a young girl after she gets kicked out of her home.

Severide struggles with the cost of helping Det. Pryma with the Martucci case. Gallo campaigns for Herrmann to represent 51 at the National Firefighter’s Association’s Winter Conference. A familiar face makes a shocking return.

Cruz feels the burden of his increased responsibilities. Kidd, Gallo and Carver get caught in the middle of a gang war on a call. Herrmann wrangles Trudy for help lifting Cindy's mood.

Brett waits for life-changing news. Herrmann encounters a psychic with a grave warning on a call. Kidd finds a new lead on the Homeland Security case.

Firehouse 51 is forced to share space with Firehouse 17. Kidd and Herrmann fight over Ritter. An arson case tests Kidd and Severide's relationship. Firehouse 51 says goodbye to one of its own.

After witnessing a domestic dispute, Brett and Violet decide to take the investigation into their own hands. Mouch vets Truck 81's new firefighter. Herrmann relies on something new to aid him on the job.