A mishap on the aerial ladder in the midst of a fire rescue leaves Mouch shaken and questioning his abilities. Kidd looks for support from Severide while Casey and Brett discuss their future.

Gallo makes a split-second decision during a dangerous fire rescue leaving Casey steaming that his direct orders were not obeyed. Kidd feels a strain in her relationship with Severide. Brett and Mackey find themselves searching for answers following a series of suspicious calls.

Mouch, Gallo, Ritter and Mackey report for training. A nasty blow to the head brings Casey unimaginable pain.

While Mouch makes an incredible save, all eyes are on a mystery man who helped save his neighbor. Casey worries about his future at the CFD.

Severide and Casey try to find the best fit for Kidd. Ritter, Gallo and Violet help plan an event for Mouch.

A video of Casey from the roof rescue goes viral. Mouch sets up a Little Free Library at Firehouse 51. Herrmann breaks protocol.

Casey makes a life-altering decision. Gallo, Ritter and Violet agree to an interview and photo shoot. Brett and Mouch launch the paramedicine program. Cruz comes closer to fatherhood.

Severide and Herrmann clash over office space. Boden looks at Pelham’s past as he considers making him permanent. Gallo’s resentment of Pelham comes to a head. Brett and Ritter force Violet to confront her true feelings for Gallo.

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.

Chief Hawkins goes above and beyond to help Brett and Violet with a problem. Kidd pursues an open lieutenant position. A blast from the past asks Mouch and Herrmann for a favor.

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.

A family friend asks Herrmann for some advice on opening a bar. Tensions run high between Emma and Violet. Kidd struggles to keep her team together.

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.

Firehouse 51 hosts a Halloween open house. Kidd and Severide help a young girl after she gets kicked out of her home.

Det. 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.

Firehouse 51 prepares for their semi-annual firehouse inspection. Brett fights to save her paramedicine program. Commander Martin Pearce asks Severide for a favor.

An annoying floater takes a romantic interest in Violet. Ritter catches a local politician in a compromising position. Mouch and Severide help Trudy with an arson investigation.

Mouch builds a classic firetruck model for the Deputy District Chief but needs some assistance from Gallo and Ritter. Brett and Violet encounter multiple victims with a strange set of symptoms. Cindy's chemotherapy results loom over the Herrmann family.

Herrmann works on becoming a better man after Cindy's cancer journey. Kidd bonds with a homeless victim on a call. Kylie takes her firefighter exams. A harrowing call takes a toll on Brett.