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.
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 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.
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.
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.
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.