Daniel Kyri

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.

Severide and Boden search to uncover whether arson was the cause of a fire at a hair salon; Mouch, Herrmann, Otis and Kidd make a startling discovery while tracking down the missing piercing nozzle from Engine 27.

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.

Brett, Foster and Kidd take a road trip to Indiana and encounter an accident involving a boys' hockey team that leaves them scrambling and relying on their instincts to save the injured; the rest of Firehouse 51 competes in the annual chili cook-off.

Foster faces blowback after pointing out a doctor's oversight; Brett helps Casey look for a new apartment; Kidd prepares Tuesday the Dalmatian for the Fire Safety Dog Competition; a serious accusation is leveled against Severide.

A serial arsonist cold case is reopened when Lt. Severide finds a connection to a recent salon fire; Firehouse 51 celebrates a retirement party.