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.
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.
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.
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.
A Naval officer who threatened to go public with tales of on-the-job sexual harassment and assault is brutally murdered, but when investigators find the allegations could be part of an elaborate scheme for money, they turn to forensic science.
Young attorney Rudy Baylor, alongside Bruiser Stone and Deck Shifflet, battles a powerful law firm led by Leo F. Drummond and his girlfriend, Sarah Plankmore, unearthing a dark conspiracy that shows how far his opponents are willing to go to win.