A mishap on the aerial ladder in the midst of a fire leaves Mouch shaken and questioning his abilities. Kidd looks for support from Severide while Casey and Brett discuss their future.
While completing a task assigned by headquarters, Boden makes an unforeseen connection. Gallo's forced to make a surprise rescue to one of their own when the firehouse is called to the site of a construction explosion. Mouch reignites an old feud.
When Firehouse 51 is called to the scene of a dangerous blaze inside a 10-story storage unit, Herrmann and Cruz find themselves trapped inside a freight elevator with all communications cut off.
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.
Casey and Severide investigate a suspicious fire at a homeless encampment. Cruz is shaken by a close call. Ritter bonds with a victim. Sylvie flirts with Grainger.
A series of suspicious fires sends 51 on a search for the cause. Casey continues down a troubling path. Mouch is looking to make his long-awaited dream come true.
A new recruit with ties to the CFD tests Serveride's patience. Violet receives a mysterious note that sends her and Brett on a hunt for the person who wrote it.
A fire breaks out at a pet food factory and Casey and Severide help the owner, Pete, get to the bottom of it. The annual garage sale takes place at 51 and everyone is on edge.
Griffin learns the truth about his father's death and reveals why he really came to visit Casey. Gallo, Ritter and Violet take steps to expand their microbrewery business.
Kidd spreads her wings as a lieutenant. Chief Hawkins rides with Ambulance 61 to learn more about Brett. Casey takes a trip out of town. A Ritter date night turns into an emergency situation.
In the show's milestone 200th episode, Casey makes a life-altering decision. Gallo, Ritter and Violet agree to an interview and photo shoot. Brett and Mouch launch the para medicine program. Cruz comes closer to fatherhood.
A major security breach in the city's computer networks forces Firehouse 51's senior leaders to take matters into their own hands. Severide gears up for an arson investigation.
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.
Gallo, Violet, and Ritter debut their microbrewery business at Winterfest. Brett prepares to present her paramedicine program to an oversight panel. Firehouse 51 gets in the holiday spirit.