Boden forces members of Firehouse 51 to pull themselves back together in the aftermath of a harrowing fire explosion. While Severide goes missing for one week too many, Casey works to track down his whereabouts. Meanwhile, Newhouse brings some unexpected news regarding one of Mills' relatives while Herrmann and Otis make some new goals regarding Molly's.

Lieutenant Severide returns to Firehouse 51, but he is clearly not his usual self. Dawson counts down the weeks until she gets started as a candidate at the Austin Firehouse. Meanwhile, Mills learns more about his father's family and Herrmann asks the potential Molly investors to come up with new ideas to turn the business around.

Tensions run high when trucks from two firehouses collide and fingers are pointed towards Cruz for his driving.

Dawson tries to strike a balance with Casey during her first day as a candidate. Meanwhile, Mills ponders an uncertain future; Severide faces his demons; and a city inspector visits Molly's.

Lieutenant Casey (Jesse Spencer) deals with the fallout of his sister Christie's (guest star Nicole Forester) impending divorce. Meanwhile, Dawson (Monica Raymund) and Mills (Charlie Barnett) settle into their new roles at Station 51. Elsewhere, Brett (Kara Kilmer) can't decide if she wants to leave Chicago and the Molly's crew still can't figure out how to get the food truck started.

Casey faces his corrupt brother-in-law and Brett goes above and beyond to help a mother in need. Meanwhile, Mills get an education on unlicensed private investigation and Dawson begins training with Herrmann.

During a house fire, Firehouse 51 rescues the owner from the cellar clutching a suspicious box, leading Lt. Severide to bring in Sergeant Voight and Detective Lindsey for further investigation.

The members of the firehouse spring into action when a helicopter explodes over a populated area.

Dawson and Casey's relationship is tested as the team responds to a truck leaking hydrochloric acid in a busy intersection. Severide learns about Brittany's past. Mouch has dating troubles.

A house fire puts a couple in danger. Dawson and Casey are pushed further apart by an unsettling surprise. The Chicago Holiday Fest gives Molly's II a chance to shine. The Chicago FD Chaplain hopes to help out a local soup kitchen with "fill the boot" donations.

The firehouse receives unsettling news when two of their own come up missing following a routine call, prompting members of Chicago P.D. to lead the search. Meanwhile, Casey and Dawson have a hard time figuring how to juggle their personal and professional lives. Elsewhere, Chief Boden and Donna struggle with news that their newborn has potential complications and they receive a surprise out-of-town visitor

Severide and Dawson discover startling evidence found at a storage unit fire that appears connected to the fire that took Shay's life. Meanwhile, the firehouse bands together when Chaplain Orlovsky is the victim of a bad car accident.

More clues emerge about the fire that killed Shay, leading Severide to a former nemesis; Shay's sister visits; Cruz is faced with a surprise; Boden tries to help his father.

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.

Interim Chief Pat Pridgen (guest star Matthew Del Negro) is brought over to temporarily fill in for Boden (Eamonn Walker), who is left to tend to his personal affairs. When tension is sparked as the result of his derisive leadership, the absence of Chief Boden (Eamonn Walker) becomes all too apparent. Meanwhile, Lieutenant Severide (Taylor Kinney) must deal with a most unwelcome addition to his squad, Brett (Kara Killmer) gets closer to a girl she previously rescued and Casey (Jesse Spencer) starts seeing a new woman, Beth (guest star Bree Williamson), but interesting complications quickly unfold.

The interim chief makes a tactical error during an apartment fire, stirring up tensions and putting careers in jeopardy.

Severide's old friend arrives, hoping for a second chance with the Chicago Fire Department. Meanwhile, Mills tries to regain his active squad status, Mouch confronts his fear about meeting his child, and Brett and Dawson set out to have a big night out.

Herrman tries to rescue a toddler from a structure fire; Mills discovers unexpected news; Brett and Cruz's relationship reaches a critical juncture; Otis is surprised by some feelings that develop.

Members of Firehouse 51 transport victims of a gas leak to nearby Chicago Med; an armed patient claiming to be carrying a deadly airborne disease forces Chicago Med into lockdown.

Mills tries to save a driver who's been seriously injured in a car accident. Meanwhile, Casey has doubts about the owner of a remodeled strip club and Hermann, Otis and Cruz prepare for the peewee hockey championship.

An apartment fire connected to a case of rape and attempted murder resembles an unsolved case in New York, so Sgt. Benson of Special Victims Unit comes to Chicago to help Intelligence with the investigation.

At Sgt. Voight's urging, a determined Lt. Casey agrees to go undercover in an effort to provide proof of Jack Nesbitt shady dealings. Meanwhile, Otis and Severide continue to disagree about the integrity of Scott Rice, causing tensions to flare between members of truck and squad. Meanwhile, Herrmann helps out a fellow member of the firehouse.

Casey puts his life on the line and digs deeper into the shady dealings of Jack Nesbitt. With members of truck and squad at odds over Rice actions in the field, Chief Boden is left to figure out how to create unity in a divided house, while Severide comes to question his own judgment. A dangerous warehouse blaze quickly gets out of control and threatens members of firehouse 51, prompting Boden and Cruz to risk everything to save their own. Elsewhere, Dawson gets some life-changing news.

Casey finds himself in dangerous territory at the center of an undercover operation to bring down a trafficking ring out of Nesbitt's strip club.

Internal Affairs investigates Firehouse 51 following a complicated call to a fire.

Boden's job is on the line as the crew of Firehouse 51 continues to search for evidence that could clear him of any wrongdoing.

A member of Firehouse 51 requires the support of the whole team to recover from a near disaster.

Boden offers to host a wedding at the firehouse after a fire ruins the ceremony, but Chief Riddle is against it and his political aspirations cause friction among the firefighters.

Severide and Patterson's differences reach a boiling point, while a visitor from Cruz's past asks for a favor.

Boden finds himself in the middle of a fiasco concerning a female neighbor he believes is setting him up.

Patterson confronts Boden about his ability to lead the firehouse.

Clues to Serena's possible whereabouts are uncovered, while Captain Patterson has news for everyone.

While a member of Firehouse 51 falls victim to a near-fatal stabbing, the other firefighters rescue a woman who attempted to commit suicide.

The city of Chicago braces for a tornado.

A tormented Herrmann is forced to make a difficult decision and Casey does his best to keep a shelter open that's housing recent tornado victims.

Mysterious threats begin to emerge throughout Chicago and the situation gets worse when news of a mass shooting brings Firehouse 51 into a dangerous scene.

Severide confronts Chili about her behavior, while Jimmy faces Antonio in the first annual "Battle of the Badges".

Severide and Cruz take matters into their own hands when Firehouse 51 responds to a suspicious call from a neighboring firehouse.

A citywide propaganda attack against Casey's run for alderman makes him reconsider his candidacy.

Severide and Cruz discover the remains of a case that may be connected to a case Severide worked on years ago.

Sylvie is threatened when she witnesses a murder.

Casey tries to use his political influence when a high school student is almost killed by a street gang.

Severide watches over Detective Holloway's son while she testifies in court as part of an undercover operation, but he's left to deal with the situation due to an unexpected turn of events.

Dawson risks her life to save a young boy from an apartment fire.

Firehouse 51 heads to the scene of a building collapse where dozens of lives are on the line.

Dawson hopes to foster Louie while a dangerous structure fire puts a member of Firehouse 51 in a dangerous situation.

Severide and Stella are on the lookout for her unstable ex.

Members of 51 end up in a dangerous situation while responding to an auto accident and Stella must make a serious decision about her ex.

Casey gets help from Susan Weller for an urgent personal matter; Severide is given an opportunity to travel with Travis Brenner; Stella saves a street kid from a tunnel fire.

Casey is forced to take extreme measures when a forklift accidentally pierces a tank of acid, causing it to spill and putting a father and daughter in danger.

Casey and Severide disagree on a potential arson case when the squad fails to save a woman from her burning house.

Dawson hits a pedestrian while responding to a call. Casey and Severide continue to investigate an arson case while Chief Boden is in New York to attend an important function.

Gabriela and Antonio's parents come to Chicago for their anniversary, while Chief Boden discovers a secret about his stepson.

Casey and Dawson apply for permanent adoption of Louie. Jeff Clarke gives Severide an interesting proposition. Otis convinces Herrmann to throw a bash celebrating the 100th anniversary of Molly's, but there are complications.

Dawson and Casey meet Louie's biological father. In other events, Severide falls back into old habits as he tries to help Anna with a bone marrow procedure, and Brett opens up to Dawson.

Louie's father throws a wrench into Casey and Dawson's family plans. Severide agrees to a bone marrow donation but a work accident throws everything into flux. Casey and Dawson try to find harmony at home. Meanwhile, Otis and Mouch decide to film a PSA encouraging people to join the Chicago Fire Department but hit a creative wall in the process.

Dawson tries to keep her emotions in check during an ambo run involving a pregnant teenager, while Casey is forced to make a split-second decision regarding two victims in need of assistance and deal with the repercussions.

A dangerous man is after Casey for an incident during a fire call.

A superior comes after Boden for making a split-second decision in an accident that overrides him.

Members of Firehouse 51 are split up and reassigned to various houses in Chicago by Chief Anderson.

Firehouse 51 responds to the scene of a blaze that puts many lives in danger, including someone related to a Chicago police officer.

Firehouse 51 is taken over by local gangsters.

When similar car accidents uncover the fact that someone may be targeting innocent people, a determined Dawson takes matters into her own hands to help push things along, meanwhile Casey tends to his Alderman's duties.

Dawson and Brett have a new trainee assigned for their shift; Severide's father pays him an unexpected visit.

Casey is reunited with an old colleague when the squad's rig breaks down in the field.

Casey takes drastic measures to help Kannell.

Cruz faces a possible suspension from the fire department for an off-duty incident.

A dangerous warehouse fire puts truck and squad at risk. Tensions rise for Dawson and Casey as Dawson's father overstays his welcome at their home. Mouch considers retirement.

With most of the squad still trapped in the warehouse fire, Chief Boden makes a risky last-minute decision to save them.

When Boden learns that the school fire in which his wife was trapped was not an accident, he pressures Severide and Casey to find the cause.

Lt. Casey butts heads with the new chief who fills in for Boden at House 51; Mullins has an unexpected surprise for Casey when he makes a risky move to stop a man from jumping off the building; Brett learns information about a friend.

While running a secret errand, Dawson finds herself trapped in a collapsed parking structure; pressure mounts on Casey as he begins taking on additional duties; Kidd grows increasingly skeptical of Hope.

Casey and Severide find themselves at odds after Casey argues with him over the best way to save a teenager entangled in barbed wire. When Casey looks to Boden for help smoothing out the situation, he comes to the realization that he will have to fix it himself. Elsewhere, Otis tries to convince Casey to participate in the beta test for an expensive piece of new firefighting equipment imported from Japan. Meanwhile, Kidd and Hope come to blows over a payroll issue and Brett goes on a date with a doctor she meets during an ambo call.

Kidd is surprised to discover she is being transferred out of the firehouse; Severide and Casey are suspicious and investigate; Otis and Herrmann discuss taking over a rundown bar; Dawson's frustration with her father reaches a boiling point.

Brett attempts to make a lifesaving decision in the field to someone near and dear to the firehouse family. In an effort to impress Lily, Otis scrambles to get everything together for the grand opening of Molly's North. Meanwhile, Boden becomes emotional following the rescue of a famous blues player from a burning apartment building and Dawson struggles to come to terms with how she has been dealing with her father.

After saving a young girl, Dawson is forced to make a tough decision when she finds out the girl's father is addicted to painkillers. Herrmann loses his cool and gets into an altercation with a police officer after responding to a call. Otis and Cruz are on a mission to find out who Brett is dating. Meanwhile, Boden is skeptical when Donna's brother Julian unexpectedly comes to town.

Dawson and Casey struggle to communicate; Brett and Kidd compete for the affections of a hazmat officer; Otis, Herrmann and Mouch search for the source of a stench that's making life difficult at Firehouse 51.

Dawson and Casey do everything they can to locate Bria's whereabouts after discovering important new information. Lt. Severide reunites with Chief Grissom, an old family friend. Meanwhile, Cruz enlists the help of Brett and Mouch to create a new tool and Kidd and Zach go on a date.

Casey and Severide disagree on the best course of action following a time-sensitive rescue; Herrmann tries to entertain his daughter on "bring your kid to work day"; Dawson joins Brett on a spa getaway; Kidd's social life gets a boost.

The photographer whose pictures of Casey and Severide during a rescue make the front page of the newspaper chronicles a day-in-the-life story at the Firehouse.

The firefighters help the police track down a bombing suspect.

A domineering husband answers for his injured wife after Casey and Dawson respond to a car accident.

Otis and Kidd respond to a call involving a residential fire only to head into danger when gunfire goes off in the house.

The members of Firehouse 51 come to terms with one of their own being injured and deal with the temporary replacement.

Boden has a lapse in judgment in the aftermath of rescuing a young boy. Kidd struggles to win the approval of Severide's mom after a surprise visit and Otis takes on new responsibilities at the firehouse.

Casey and Severide assist the FBI with an undercover mission; Kidd tries to help Severide come to terms with recent developments.

Casey grows skeptical of Cordova when a large amount of money turns up missing at the property of Mexican drug cartel.

Boden and Severide receive a surprise package after saving a girl from a car accident.

Severide is surprised when Renee Royce returns to the firehouse; Casey helps Chief Boden in his latest pursuit; Kidd regrets a decision regarding Severide; Herrmann disagrees with Lt. Colannino over how to coach their sons' basketball team.

Boden takes a big step in the pursuit of a major career decision. Kidd becomes increasingly distrustful of Renee's motives with Severide. Herrmann has trouble bouncing back after a tragedy.

Boden's chances for a promotion are met with potential complications, leading him to take matters into his own hands. 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.

Casey struggles with his personal life; the firehouse welcomes a new member; Boden clashes with the new assistant deputy commissioner.

A raging fire consumes a 25-story apartment building complex, trapping victims on the top floors.

Boden becomes skeptical of Gorsch's motives; Severide gets involved in a difficult situation following a child's rescue from a car wreck; Foster is tasked with giving Cruz personal advice.

A series of explosions hit Chicago; Herrmann adjusts to his new duties; Kidd is visited by an old friend.

Casey investigates the cause of a trailer park fire; Boden reaches his breaking point; Mouch, Herrmann and Cruz wonder why Molly's isn't living up to expectations.

Gorsch takes over Boden's morning meeting at Firehouse 51 and goes out on calls in his place; Brett and Foster respond to a call about a Halloween prank getting deadly serious.

Severide struggles to process his father's death; Brett thinks a teenage driver in a car accident is hiding something.

Firehouses 51 is called in to battle a structure fire that places everyone in peril.

A car pile-up impacts someone dear to the firehouse family. Brett and Foster encounter a harrowing call while Kidd and Severide find their relationship being tested.

Casey and Naomi escape a deadly fire in his apartment. Brett puts together a team to create a community fire safety presentation but they struggle to make it engaging. Severide and Kidd are at a crossroads.

Foster faces blowback after pointing out a doctor's oversight. Brett helps Casey look for a new apartment. Kidd prepares Tuesday the Dalmatian for the Fire Safety Dog Competition. A serious accusation is leveled against Severide.

When the firehouse is called to a motorcycle crash, Casey and Severide sense that the details don't add up. A rift develops between Mouch and Otis. Brett, Foster and Kidd work to secretly fix a dent in the ambulance bumper.

Cruz leads the charge in getting the firehouse to gear up for the Polar Plunge. Herrmann has a hard time bouncing back after dealing with a tough call. Foster's personal relationships begin to interfere with her job.

Brett, Foster and Kidd take a road trip to Indiana and encounter an accident involving a boys' hockey team that leaves them scrambling and relying on their instincts to save the injured. The rest of Firehouse 51 competes in the annual chili cook-off.

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.

Casey struggles after experiencing a narrow miss on a call. Otis wins a unique sporting opportunity in a raffle. Grissom turns to Severide for assistance when the mayor's office sends a task force to Firehouse 51.

Tensions run high between Casey and Herrmann after the firehouse responds to an apartment complex fire. After discovering something extremely suspicious during the call, Kidd and Severide do some investigating and get CPD on the case.

Severide gets angry at Cruz when he feels his orders were disobeyed in the field. Boden reconnects with an old high school friend during a call to a house fire. Herrmann has issues when one of his favorite knick-knacks from Molly's goes missing.

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 Boden search to uncover whether arson was the cause of a fire at a hair salon. Mouch, Herrmann, Otis and Kidd make a startling discovery while tracking down the missing piercing nozzle from Engine 27.

A serial arsonist cold case is reopened when Lt. Severide finds a connection to a recent salon fire. Firehouse 51 celebrates a retirement party.

Severide and Kidd continue to investigate Benny's old arson case. Unexpected news leads Brett to ponder a big decision. 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.

Casey struggles to get Boden to sign off on an energetic new recruit; Foster extends an olive branch to her irritating new medic; Otis inspires Herrmann to seek new partners at Molly's.

Brett and Foster question the suspicious circumstances surrounding an attack at a juvenile detention center; new technology at Firehouse 51 tests everybody's patience; Kidd is chosen to represent the district at a leadership conference.

A 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; Severide suspects something bigger is happening.

Kidd must prove herself at the National Firefighter Leadership Conference, while the rest of Firehouse 51 is called to two eerily similar car wrecks. Mouch tries to keep the firehouse informed by starting a newsletter. Cruz deals with a heartbreak.

Cruz and Severide suspect foul play when a fire started by an elderly woman turns deadly. Kidd, Foster and Brett create a women's-only lounge. Firehouse 51 celebrates some good news.

Severide must make a tough decision about the future of his career at Firehouse 51. Herrmann deals with the consequences of his temper after a run-in with a Chicago police officer. Cruz is excited to demonstrate the Slamigan at the Firefighting Expo. Commissioner Grissom returns.

Severide begins his assignment at the Office of Fire Investigation and gets off on the wrong foot when, despite his orders, he reopens an old case. When the cause of an apartment fire hits close to home, Herrmann is on a mission to get to the bottom of it. Kidd finds herself burning the candle at both ends.

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.

Members of Firehouse 51 are dismayed to learn their boundaries have been redrawn to overlap with an adjacent station and problems quickly arise. Casey and Gallo hunt a missing piece of equipment. Brett and Foster find themselves at odds. Mouch tries the find the recipient of a mysterious letter he discovers.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20. All under the same roof, Casey clashes with Capt. Delaney while Foster, Kidd and Brett fear Capt. Leone has it out for them. Boden mulls a procedural overhaul.

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.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51. Boden and Severide are asked to make peace with an old foe for the greater good. Brett receives family news while Foster plans a party with friends.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin. Brett's conflicted when her birth mother gets serious about tracking her down. Severide misunderstands his role as Cruz's best man. Mouch bites off more than he can chew.

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.

Boden is on edge after starting a new fad diet. Casey and Severide disagree on a call. Brett's birth mother shares life-altering news. A familiar face has a proposition for Herrmann.

Things get personal for Casey and Gallo in the aftermath of a suburban house fire involving a mother and her young son. Herrmann campaigns for more respect. Kidd has an idea for giving back to her community.

Lt. Severide teams up with Seager and the OFI when a motel structure fire turns suspicious. Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own. Brett continues to get invested in her birth mother, Julie.

Tension builds when a group of rabble-rousers attempt to lock down the firehouse. Brett is faced with a monumental decision. Cruz readies himself for a big day. Gallo and Ritter attempt to launch Firehouse 51 into the social media age.

When one of 51's own gets injured on a call, Lt. Severide becomes obsessed with helping out. Foster contemplates a big decision. Kidd is concerned for one of her high school trainees.

As 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.

A mishap on the aerial ladder in the midst of a fire leaves Mouch shaken and questioning his abilities. Kidd looks for support from Severide while Casey and Brett discuss their future.

While completing a task assigned by headquarters, Boden makes an unforeseen connection. Gallo's forced to make a surprise rescue to one of their own when the firehouse is called to the site of a construction explosion. Mouch reignites an old feud.

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.

Gallo makes a split-second decision during a dangerous fire rescue leaving Casey steaming that his direct orders were not obeyed. Kidd feels a strain in her relationship with Severide. Brett and Mackey find themselves searching for answers following a series of suspicious calls.

Casey and Severide investigate a suspicious fire at a homeless encampment. Cruz is shaken by a close call. Ritter bonds with a victim. Sylvie flirts with Grainger.

A call to a familiar location brings back mixed emotions for Severide; Herrmann heads out for a vacation; Casey is not thrilled with his replacement

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

A series of suspicious fires sends 51 on a search for the cause. Casey continues down a troubling path. Mouch is looking to make his long-awaited dream come true.

A new recruit with ties to the CFD tests Serveride's patience. Violet receives a mysterious note that sends her and Brett on a hunt for the person who wrote it.

While Mouch makes an incredible save, all eyes are on a mystery man who helped save his neighbor. Casey worries about his future at the CFD.

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.

A fire breaks out at a pet food factory and Casey and Severide help the owner, Pete, get to the bottom of it. The annual garage sale takes place at 51 and everyone is on edge.

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

The firehouse reacts to some exciting news, a mysterious stranger arrives and a shocking call takes Severide's breath away.

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

A video of Casey from the roof goes viral. Mouch sets up a Little Free Library at Firehouse 51. Herrmann breaks protocol.

Griffin learns the truth about his father's death and reveals why he really came to visit Casey. Gallo, Ritter and Violet take steps to expand their microbrewery business.

Kidd spreads her wings as a lieutenant. Chief Hawkins rides with Ambulance 61 to learn more about Brett. Casey takes a trip out of town. A Ritter date night turns into an emergency situation.

In the show's milestone 200th episode, Casey makes a life-altering decision. Gallo, Ritter and Violet agree to an interview and photo shoot. Brett and Mouch launch the para medicine program. Cruz comes closer to fatherhood.

A major security breach in the city's computer networks forces Firehouse 51's senior leaders to take matters into their own hands. Severide gears up for an arson investigation.

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

Severide and Herrmann clash over office space. Boden looks at Pelham's past as he considers making him permanent. Gallo's resentment of Pelham comes to a head. Brett and Ritter force Violet to confront her true feelings for Gallo.

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.

Stella Kidd returns to Firehouse 51. The team must work together to put out a potassium fire in a tunnel. After that incident, Ritter begins to worry about a young cop who witnessed the fiery death of a truck driver.

On a call with Station 37, a firefighter is struck by a power line and decides to lash out after her injury; Brett is visited by Scott and Amelia; Violet gets a surprise envelope; the rest of 51 enters a contest.

Boden, Kidd, and Severide work together to protect one of their own; at the Fire Academy, Herrmann meets an inspiring young man; talk of the annual CFD Gala dominates the firehouse.

Severide and Seager join forces to investigate a fire in a young woman's home. Pelham moves into 51's infamous office. Kylie helps Kidd with Girls on Fire.

Chef Hawkins helps Brett and Violet with a problem. Kidd is looking for a position as a lieutenant. Mouch and Herrmann are asked for a favor.

Following an injury in the aftermath of an industrial fire, Severide and Seager work together to investigate an anonymous tip. Kidd searches for the right person to fill the open spot on Truck 81.

Cruz forms a bond with a young immigrant boy he meets while fighting an apartment fire. Squad makes plans to prank the newest member of their team. Hawkins and Violet struggle to keep their relationship a secret.

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.

Firehouse 51 must band together when one of their own is taken hostage.

Firehouse 51 tackles a fire caused by a dropped jet engine and one of their own is accused of a theft related to the incident. Kidd and Boden disapprove of Kylie's potential new love interest.

A family friend asks Herrmann for some advice on opening a bar. Tensions run high between Emma and Violet. Kidd struggles to keep her team together.

Mouch and Ritter work together to solve a murder mystery; Severide and Cruz tackle a food truck fire; Gallo goes to see Hawkins about Violet.

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.

Javi spends a couple of shifts at Firehouse 51. Kidd and Carver work together to help Carver's former boss. As Hawkins and Violet's relationship blossoms, Gallo turns his attention elsewhere.

Kidd recruits Carver, Capp and Tony to help prepare her new lieutenant's quarters. Severide and Detective Pryma reluctantly pair up to work a police investigation. Firehouse 51 comes together to fight a movie theater fire.

Kidd gets a glimpse into Carver's chaotic personal life. Mouch and Herrmann get an unexpected gift.

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

Severide and Kidd investigate an explosion at a jewelry store. Cruz and Chloe take steps to make Javi a permanent part of their family. Gallo, Ritter, and Mouch try to bond with Carver.

Herrmann is tasked with fulfilling a man's dying wish. Kidd reflects on her Girls on Fire program after one of her students graduates from the Fire Academy. A heckler harasses Firehouse 51.

Detective Pryma asks for Severide's help on a case involving explosives; Gallo and Carver clash after Gallo improvises on a call; Violet encourages Brett to start dating again.

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.

Det. Pryma's case comes to an explosive end with Kidd and Carver's lives in danger. Brett installs an infant Safe Surrender Box at 51. Violet is determined to take Emma down.

Firehouse 51 prepares for their semi-annual firehouse inspection. Brett fights to save her paramedicine program. Commander Martin Pearce asks Severide for a favor.

Truck and Squad clash after a tense call rescuing a doomsday prepper. Herman struggles with Cindy's diagnosis. Violet gives Brett and Gallo dating advice.

Firehouse 51 helps Herrmann put on a school fundraiser. Carver's troubled brother comes to town. A grateful citizen is determined to thank Brett and Severide for saving his life.

An annoying floater takes a romantic interest in Violet. Ritter catches a local politician in a compromising position. Mouch and Severide help Trudy with an arson investigation.

Kidd, Seager and Carver investigate a fire at the city stables. Kylie clashes with some of the firefighters over changes due to budget cuts. Herrmann struggles to keep it together as Cindy's condition worsens.

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.

Mouch builds a classic firetruck model for the Deputy District Chief, but quickly needs some assistance from Gallo and Ritter. Brett and Violet encounter multiple victims with a strange set of symptoms. The results of Cindy's chemotherapy loom over the Herrmann family.

A familiar person returns to Firehouse 51 to serve with Kidd on a special task force. Tony is close to breaking the CFD's perfect attendance record. Old grudges resurface when Gallo reunites with a family member.

Boden, Ritter, Herrmann and Kidd work together to take down a local politician responsible for a chemical fire. After his aunt's accident, Gallo worries about their future. Brett steps in to perform Dylan's magic show when he's out of town

Herrmann works on becoming a better man after Cindy's cancer journey. Kidd bonds with a homeless victim on a call. Kylie takes her firefighter exams. A harrowing call takes a toll on Brett.

Carver deals with the fallout of his arrest. Brett searches for closure with the baby she rescued. Capp weasels his way into the Firehouse 51 group chat.

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.

Brett, Foster and Kidd take a road trip to Indiana and encounter an accident involving a boys' hockey team that leaves them scrambling and relying on their instincts to save the injured. The rest of Firehouse 51 competes in the annual chili cook-off.

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51. Boden and Severide are asked to make peace with an old foe for the greater good. Brett receives family news while Foster plans a party with friends.

Lt. Severide teams up with Seager and the OFI when a motel structure fire turns suspicious. Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own. Brett continues to get invested in her birth mother, Julie.

Brett and Foster question the suspicious circumstances surrounding an attack at a juvenile detention center; new technology at Firehouse 51 tests everybody's patience; Kidd is chosen to represent the district at a leadership conference.

Sylvie is threatened when she witnesses a murder.

Carver deals with the fallout of his arrest. Brett searches for closure with the baby she rescued. Capp weasels his way into the Firehouse 51 group chat.

As 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.

Casey faces his corrupt brother-in-law and Brett goes above and beyond to help a mother in need. Meanwhile, Mills get an education on unlicensed private investigation and Dawson begins training with Herrmann.

Herrmann works on becoming a better man after Cindy's cancer journey. Kidd bonds with a homeless victim on a call. Kylie takes her firefighter exams. A harrowing call takes a toll on Brett.

The firehouse receives unsettling news when two of their own come up missing following a routine call, prompting members of Chicago P.D. to lead the search. Meanwhile, Casey and Dawson have a hard time figuring how to juggle their personal and professional lives. Elsewhere, Chief Boden and Donna struggle with news that their newborn has potential complications and they receive a surprise out-of-town visitor