Mo Gallini

Following the gutsy firefighters, rescue squads and paramedics of Firehouse 51. No field is more dangerous yet so exhilarating, but the personal lives of these men and women provide close competition.

Casey falls under the thumb of a rogue cop after a horrific car crash, while new girl on the block Nicki pays Severide special attention.

Darden's widow publicly blames Severide for her husband's death and Casey makes a decision about his future with Hallie.

Chief Boden comes under fire when the press blames him for the death of a homeless man, while Shay has a nasty run-in with her ex-girlfriend.

Air Force One declares an emergency; with Paul seriously injured after being shot protecting Jack, Audrey's feelings toward Jack turn cold.

Casey loses his rag and comes to blows with Detective Voight, while Dawson's career hangs in the balance after her questionable conduct on a call.