A month after a devastating loss, firefighters of the Chicago firehouse 51 fight to work past it and continue to serve the city.

An injury sidelines Herrmann. Severide carries out a victims last wish after failing to save him. Casey wants to restart things with Hallie. The fire crew are having issues with a goat being on their insignia.

Casey is pressured into recanting a statement when he learns a drunk driver is the son of a veteran CPD detective. Severide learns the severity of his injuries. Mills wants out of the family business to pursue firefighting.

Boden faces backlash after his decision to pull his team from a burning warehouse. Voight steps up his threats against Casey. Severide suspects arson threats against an elderly lady. Leslie has an encounter with an old flame.

Kelly seeks help from his ex in acquiring painkillers. Herrmann gets stuck in a pyramid marketing scheme. The feud between Casey and Detective Voight becomes personal.

Casey reaches a boiling point with Detective Voight and gets an angel to help take him down. Dawson faces off with the suspension board.

It's Thanksgiving and Boden order's a drug test for the 51, putting Severide in a tough position. Cruz's brother is injured in a gang shooting. Otis starts a podcast. Leslie's ex-girlfriend visits the firehouse.

Mills considers leaving the 51 after encountering the remains of a victim. Leslie is confronted by Clarice's husband. Severide develops an addiction to painkillers. Dawson suspects a mother poisoning her daughter.

An injury on the job forces Vargas to retire. Cruz seeks to pull his brother from a gang and the price is high. Severide starts a relationship with a woman he saved on a job.

The 51 crew is under investigation when a woman accuses the firemen of stealing a diamond necklace from her home. Cruz makes a risky move to pull Leon out of a gang. Things get serious with Kelly and Renée.

Casey sees his mom in prison.

Dawson is stuck in a love triangle between Casey and Mills. Casey is asked to speak at his mother's upcoming parole hearing. Severide comes clean to Boden about his arm injury.

Kelly considers moving to Madrid with Renée and learns the risks of surgery. Matt speaks for his mother at the parole hearing. Boden races against the clock to save Ernie. Leslie offers Clarice a place to stay.

One month later, Severide returns to the station after a full recovery, only to find out that the person who filled in for him is his ex-fiancée's brother. Otis reconsiders his decision to transfer. Herrmann, Gabby and him buy a bar. Casey's mother is released on parole and moves in with her son. Gabby sends a text to the wrong person. Clarice goes in labor. Also, there's a spike in heroin overdoses and Gabby's brother Antonio is determined to go after the guys who are behind it, no matter what it costs him.

In the wake of a shooting that placed her brother in the ER, Gabriela seeks help from an old enemy. Herrmann learns his silent partner is a thug. Leslie and Clarice face a custody lawsuit with Daniel. Casey seeks closure.

To make up for the crushing feeling of guilt, Cruz becomes overzealous at work, to the point where he puts a colleague's life at risk. Otis, Herrmann and Gabby find a hidden safe in their bar. Kelly finally confronts Renee Whaley. Casey meets with his sister to decide what to do about their mother, who has been acting quite recklessly. Meanwhile, Leslie struggles to prove she could be a fit mother to Clarice's baby, but to make matters worse, a homeless man sticks her with a needle, possibly exposing her to HIV.

Shay decides she wants to have a baby. Gabby, Herrmann and Otis finally name their bar. Kelly's father visits Firehouse 51. Boden hosts a Fire Academy Gala. The truth about the death of Mills' father is revealed.

Peter starts looking into his father's death and he confronts Benny Severide about it, while Chief Boden asks Gabriela to keep a secret. After an unexpected source tells her more about the sperm-donating process, Shay decides to take a different approach at having a baby. Kelly wants to help an old man whose restaurant has been put on fire as an intimidation method, but nothing is at it seems. Heather invites herself to dinner with Matt.

Kelly pushes to get Peter on the Rescue Squad, while chewing out Casey for being around Darden's widow. A tragedy strikes the fire crew. There is a shooting at the firehouse. Herrmann tries to reconnect with his family.

Mills focusing on making squad causes a rift in the 51. Herrmann's wife comes to the firehouse and experiences complications. Shay and Dawson are having issues with the new ambulance candidate.

Severide faces a bizarre accusation and the 51 is ordered to attend a sexual harassment sensitivity seminar. Matt and Hallie reunite. Voight is released from prison and reinstated. Mills sparks Hadley's envy.

Severide digs into Tara's past to fight a case against him and learns this wasn't her first rodeo. Peter asks Gabby to move in with him. The 51 meets a young girl who Boden knew from a past. A personal tragedy hits Casey.

Casey must set aside his differences with Voight to find Hallie's killer. Peter is reeling from the truth about his father's death. Leslie prepares for insemination. Otis hires his Russian cousin as a waitress as Molly's is set to open.

The 51 are sent to a prison to do a job and all hell breaks loose. Cindy goes into labor. Shay learns the results of her pregnancy. Mills learns about his chances to make squad. A familiar face returns to Severide's life.

Boden learns his firehouse is in danger of getting shut down. Severide is being targeted by an arsonist. Mouch brings his new girlfriend to the firehouse. Molly's is facing a competition from a new sports bar down the street.

The threat of an arsonist with a vendetta against the firehouse looms and Casey struggles with the repercussions of Heather Darden's accident.

Severide is convinced he knows the arsonist's identity.

Internal issues threaten to derail Engine Company 51.

The future is uncertain for more than just Boden and Firehouse 51.

While out on a jog, Severide comes across a secluded and empty construction site and encounters a young boy who has been trapped in a backhoe loader and is in dire need of assistance. Boden and McLeod continue to butt heads about the future of the firehouse and Boden breaks news about his future to Casey. Meanwhile, it's election day for the union presidency and Mouch and Greg Sullivan have a debate on Otis' podcast. With rival bar Game Day's future in peril, the finger is being pointed at Molly's.

McLeod continues to pressure Chief Boden, threatening to close Station 51, since he failed to retire as planned. "Mouch" steps up to pressure the union leader to preserve the station.

When the shooting of a young girl happens in their neighborhood, Cruz and his brother Leon are forced to think about the gang they have tried to escape. The battle between Chief Boden and McLeod continues to escalate and Isabella convinces Mills to dress up for a fancy gala. Meanwhile, Lt. Casey is sad Dawson won't be coming by as much now that his parental duties are over, Shay is fed up with the firehouse and digs in deeper with Devon and Zoya's visa is expiring, prompting her to come up with an idea.

Battalion Chief Boden prepares to counterattack McLeod in a final effort to save the firehouse from closure and the romance between Dawson and Casey escalates. Leon is making progress in the gang murder investigation, but Cruz cannot stand being left in the dark by Voight, fearing for his brother's safety. Meanwhile, Severide and Katie bond to make up for lost time and Otis feels uncomfortable living with Severide and Shay after Devon's latest escapade.

All seems lost with firehouse 51 on the verge of closing its' doors, thanks in no small part to Gail McLeod, but Chief Boden and the rest of the house refuse to allow themselves to sit by and let it happen. An emergency call to an apartment structure fire tests everyone's limits and puts the squad in harm's way. Meanwhile, Dawson receives some life-changing news and union president Greg Sullivan makes headlines, which has an immediate impact on Mouch.

Lt. Casey returns to work at Firehouse 51 after nearly being killed in a building collapse and Shay meets Allison Rafferty, her new partner, who is friendly to everyone except her. Dawson begins her rigorous training at the Chicago Fire Academy, while Lt. Severide prepares for his stint as instructor. Meanwhile, Clarke stubbornly does not speak with the police about the murder in which he is the prime suspect and the future of Molly's looks bleaker than ever.

Lieutenant Casey tries to convince himself and everyone around him that he is one hundred percent healthy following his near-death incident in the line of duty. Shay, not wanting to delve into the emotionally traumatic incident, continues to elude a lawyer who wants to speak with her about Darryl's suicide. Meanwhile, Otis and Katie bond over board games, Boden helps out a woman with a negligent landlord and Dawson notices fellow recruit Rebecca Jones undertaking some interesting test-taking techniques at the Academy.

When a drunk driver knocks down a transformer, the entire neighborhood is left without power on a frigid Chicago night and members of Firehouse 51 step up to lend their much needed help. While many from the community ride out the night at the station, in the midst of such close quarters, romances speed up and tempers flare. Meanwhile, Casey continues to lie to both himself and Dawson about his condition and the stakeholders in Molly's bicker about the bar's direction.

Severide feels sidelined as he leaves Detective Lindsay and the Intelligence Unit to do their job and locate his sister Katie. Shay gets an unusual tip from Chicago Blackhawk players Brent Seabrook and Duncan Keith, who make friends with Clarke and stop by Molly's. Meanwhile, Casey learns more about his head injuries after another close call and Dawson pushes hard to pass the physical test at the Academy.

Severide is getting impatient with the police as Vince Keeler walks free. Meanwhile, the house pulls out all the stops to save a girl trapped inside a donation bin, Mouch learns that Boden's secretary Connie is not someone to mess with and the squad and truck are called to a serious high rise fire inside a 20-story downtown office building.

Lt. Severide (Taylor Kinney) hits the top of the list as Det. Lindsay (guest star Sophia Bush) starts calling in suspects with the clearest motives to make the guy who kidnapped Katie disappear. Meanwhile, Jones (guest star Daisy Betts) is still having trouble fitting in as word of her disruptions reach the fire department's headquarters. Elsewhere, Herrmann (David Eigenberg) celebrates his twentieth anniversary with his wife, but no one supports his idea on the gift he intends to give.

Lt. Severide (Taylor Kinney) is reminded of his own past by a man he saves from a car accident (guest star W. Earl Brown) and feels compelled to help him. Elsewhere, Lt. Casey (Jesse Spencer) and Chief Boden (Eamonn Walker) grapple with how to dock Jones (guest star Daisy Betts) per her father's orders. Meanwhile, Mouch (Christian Stolte) and Dawson (Monica Raymund) have troubles with the opposite sex and an emotional call to duty creates ripples throughout Firehouse 51.

Lt. Severide sticks his neck out for Dave Bloom, a fellow firefighter from Denver who is troubled by addiction. Elsewhere, Dawson and Shay leave town for a "girl's weekend" at a cabin in the woods. Meanwhile, Jones struggles with the knowledge that her father is pressuring Chief Boden about her career path and Mouch's Internet dating profile gets an upgrade with the help of Mills and the guys.

A suicide note is delivered to a surprised Dawson (Monica Raymund) and Lt. Severide (Taylor Kinney) digs deeper into Bloom's (guest star W. Earl Brown) dark past. Elsewhere, Chief Boden (Eamonn Walker) learns shocking news, and with the help of Shay (Lauren German), Lt. Casey (Jesse Spencer) goes on the search for a life-changing item.

An explosion at a hospital where Casey and Dawson are volunteering for a charity run sends Chicago into chaos.

With everyone's support, Dawson (Monica Raymund) makes final preparations to retake the fireman's exam, but a call to the field may throw a major wrench into her plans. Elsewhere, Lt. Casey (Jesse Spencer) has an important matter to discuss with Antonio (guest star Jon Seda, "Chicago P.D."). Meanwhile, Lt. Severide (Taylor Kinney) and the firehouse welcome Rick Newhouse (guest star Edwin Hodge), the latest addition to the squad, Shay (Lauren German) gets an uninvited surprise guest and Chief Boden (Eamonn Walker) makes a bold move.

A fire at a boarding school shakes up Lt. Severide; Lt. Casey tries to help Dawson; Mills looks into his father's past.

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.

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.

Mills considers leaving the 51 after encountering the remains of a victim. Leslie is confronted by Clarice's husband. Severide develops an addiction to painkillers. Dawson suspects a mother poisoning her daughter.

Shay decides she wants to have a baby. Gabby, Herrmann and Otis finally name their bar. Kelly's father visits Firehouse 51. Boden hosts a Fire Academy Gala. The truth about the death of Mills' father is revealed.

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

Peter starts looking into his father's death and he confronts Benny Severide about it, while Chief Boden asks Gabriela to keep a secret. After an unexpected source tells her more about the sperm-donating process, Shay decides to take a different approach at having a baby. Kelly wants to help an old man whose restaurant has been put on fire as an intimidation method, but nothing is at it seems. Heather invites herself to dinner with Matt.

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.

All seems lost with firehouse 51 on the verge of closing its' doors, thanks in no small part to Gail McLeod, but Chief Boden and the rest of the house refuse to allow themselves to sit by and let it happen. An emergency call to an apartment structure fire tests everyone's limits and puts the squad in harm's way. Meanwhile, Dawson receives some life-changing news and union president Greg Sullivan makes headlines, which has an immediate impact on Mouch.

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.

An explosion at a hospital where Casey and Dawson are volunteering for a charity run sends Chicago into chaos.

Casey sees his mom in prison.