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.

An unexpected visit throws Casey for a loop; Severide sets out to exonerate a wrongly convicted arsonist; Kidd pays the price for burning the candle at both ends; Cruz goes on a mission to fix one of Otis's old toys.

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.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

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.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.