Daniel Kyri

When one of 51's own gets injured on a call, Severide becomes obsessed with helping out; Foster contemplates a big decision; Kidd is concerned for one of her high school trainees.

The mattress factory fire spirals out of control; truck and squad lay it on the line in hopes of getting the trapped victims out alive.

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 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.

Tension builds when a group of rabble-rousers attempts to lock down the firehouse; Brett is faced with a monumental decision; Cruz readies himself for a big day; Gallo and Ritter attempt to launch Firehouse 51 into the social media age.

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.