Reeling from Dawson's continued absence, Casey makes a rash move during a rescue, while Brett struggles with a series of replacement partners; meanwhile, Boden faces scrutiny from Commissioner Grissom, who sends his deputy to monitor Firehouse 51.
Firehouse 51 bands together to fight a raging fire on the 20th floor of the residential high-rise where Jay and Will Halstead's father lives and has gone missing; in the midst of the chaos, Brett learns unsettling information about her new partner.
Severide investigates a victim's motives after rescuing him and his child from a car accident; Boden clashes with Gorsch over appointing a new lieutenant; Mouch reaches out to a fellow firefighter; Cruz discovers he has a new admirer.
Herrmann faces hazing in his new role as lieutenant; Foster suspects a young gymnast's injury is more than meets the eye; Severide is jealous of Kidd's best friend; Casey and Boden turn to P.D. after treating two victims who have similar injuries.
Casey helps a reporter uncover the truth behind a trailer park fire; Boden attempts to make peace with Grissom; Hermann, Otis and Kidd take action when Molly's receives a bad Yelp review; Severide reaches out to his father for a favor.
Gorsch continues his reign of terror at Firehouse 51, taking over Boden's morning meeting and going out on calls in Boden's place; Brett and Foster respond to a call where a Halloween prank has turned deadly serious.
Kidd and the team embark on a mission to help Severide as he struggles to process his father Benny's death; Brett suspects a teenage driver in a car accident is hiding something.
Severide lands in grave danger when Firehouse 51 battles a risky structure fire; Casey lends another helping hand to Naomi, the investigative reporter; Herrmann, Mouch, Otis and Cruz search for a tantalizing memento from Boden's past.
Firehouse 51 responds to a massive freeway accident that impacts someone close to them; Foster runs into someone from her past after a harrowing call; Casey and Naomi grow closer; Severide and Kidd's relationship is tested.
Casey and Naomi fight to escape a raging fire in Casey's apartment; Brett and the team struggle to create an engaging community fire safety presentation; Severide and Kidd's relationship reaches 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.
Casey further investigates a motorcycle accident at the request of the victim's son; Kidd, Foster and Brett bond while helping Kidd fix a mistake; Mouch and Otis have a falling out after Otis' teasing hits a sore spot.
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; Sgt. Hank Voight suspects a firefighter may be involved, and with Boden's support, he recruits Cruz to go under cover 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; when a little boy mysteriously shows up at the station, 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.