In the Season 5 finale, a warehouse fire puts the team at risk; Dawson's dad overstays his welcome; Casey fights for his first responders bill; Mouch makes a major life decision; and Herrmann goes to tremendous lengths to make a young boy smile.
Cruz finds himself in a bad spot when an off-duty incident begins to unravel, prompting Mouch to step in and offer help in hopes of avoiding serious consequences from the CFD. In other events, Casey goes head-to-head with a big politician to get his measure for first responders passed; Lt. Severide makes life difficult for new team member Jason Kannell; and Dawson gets an unexpected visit from her father.
Casey goes to drastic measures to help Kannell; Severide helps an old widow come to terms with letting go, but realizes he may be the one needing help; Otis and Cruz find a new roommate to move in; and Dawson and Brett get crafty to save a young girl.
When the squad's rig breaks down in the field, Casey reunites with his old friend and colleague Jason Kannell from Squad 6, whose crew gets assigned a temporary change of quarters until the rig issue is resolved. Dawson and Brett serve their time in retraining, both tackling the class in unique ways. Severide tries to remedy what's 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 replacement will last.
Casey discovers a new crack house on the block that's harboring a female junkie; Dawson and Brett are assigned a new trainee for the shift; Severide's father unexpectedly visits; and Herrmann deals with family issues involving his son.
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; Severide does everything he can to make Anna feel welcome; Herrmann, Kidd and Dawson decide to have Molly's included as a stop in a pub crawl despite strong concerns from Otis; and Casey tends to his alderman's duties when a persistent constituent asks for his help in resolving an issue.
When a turf war escalates, truck and squad members find themselves caught in the middle as unsuspecting hostages when a group of armed gang members take cover and assume control over Firehouse 51. The situation turns even more dire when one of the infiltrators is wounded.
A fire at an old factory-turned-living/working space traps countless people, including police detective Alvin Olinsky's daughter; and the influx of victims from the scene tests the doctors and nurses at Chicago Med. In the aftermath, the building owner steps forward to cooperate with the investigation, but the situation takes a sudden and unexpected turn.
Chief Anderson reassigns members of Firehouse 51 to other stations around town; and Boden fights to repair the situation, but it may be out of his control. In other events, Severide toils over an important decision.
Boden and House 51 face the heat after he makes a split-second decision at an accident scene that undercuts a superior; Severide contemplates a major decision; Herrmann does a good deed; and Brett looks to make some personal changes.
CPD intervenes when Casey and the squad are targeted by a man who has a grudge against them; a pal of Severide's father shadows the squad; Brett's relationship with Antonio hits some turbulence: his ex-wife; and Casey has a gift for Dawson.
Dawson has difficulties keeping her emotions in check during a run with a pregnant teen; Casey makes a split-second decision at a fire scene when two victims both need life-saving assistance; and Severide and Anna bond during her recovery.
Severide agrees to donate bone marrow, but an accident throws everything into flux; Casey and Dawson seek some peace at home; and Otis and Mouch film a PSA encouraging folks to join the fire department.
Dawson and Casey meet with Louie's biological father; Severide falls back into bad habits when his efforts to help Anna don't go as planned; Brett opens up to Dawson; and members of Firehouse 51 become competitive.
Casey and Dawson face a hurdle in their quest to adopt Louie; Severide receives an interesting proposal from a firefighter-turned-medical student; and Otis convinces Herrmann to throw a bash in honor of Molly's 100th anniversary.
Dawson and her brother Antonio host a family reunion when their parents come to Chicago for their anniversary; Boden takes matters into his own hands after a secret involving his stepson comes to light; Casey tries to save a young boy at a warehouse; and Otis and Kidd square off at a mud race.
Casey is unable to save a woman from a burning house; and he and Severide disagree over the fire's cause. Also: Herrmann is out to catch a mystery tagger who's targeting the firehouse; Boden receives a surprise visitor; and Dawson and Brett respond when a teen boy is injured during a romantic homecoming proposal.
Casey, while inspecting a warehouse as part of his alderman duties, finds himself at the scene of a hazardous spill; Dawson and Brett help an elderly woman with a difficult senior advocate; Mouch and Brett continue with their secret project; and Otis has big news.
Casey seeks help with a personal matter from Susan Weller; a rich party guy wants Severide to travel with him; Stella tries to help a sick street kid; and Otis and Herrmann share their concerns about Molly's lack of customers.
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; and Brett and Mouch set aside their writing differences for the greater good.
In the Season 5 premiere, Severide and Stella search for Grant, who's AWOL from Chicago Med; Dawson questions her career path; Casey's relationship with his political consultant cools; and Borrelli's anger at Boden over his brother's death boils over. In other events, Mouch and Brett partner on a new venture.