Severide (Taylor Kinney) feels sidelined as he leaves Detective Lindsay (guest star Sophia Bush) and the Intelligence Unit to do their job and locate his sister Katie (guest star Brittany Curran). Shay (Lauren German) gets an unusual tip from Chicago Blackhawk players Brent Seabrook and Duncan Keith, who makes friends with Clarke (guest star Jeff Hephner) and stop by Molly's. Meanwhile, Casey (Jesse Spencer) learns more about his head injuries after another close call and Dawson (Monica Raymund) pushes hard to pass the physical test at the Academy.moreless
Chicago Police Department's newly-minted Intelligence Unit leads investigation into a string of murders possibly related to a Colombian drug gang; Desk Sergeant Trudy Platt has Officer Kim Burgess run an errand for her; Veteran undercover officer Alvin Olinsky recruits a rookie to the unit; and the attempted arrest of the assassin leads to tragedy that cost Intelligence Unit one of their own people.moreless
Thanksgiving at the firehouse includes a 10-car pileup, a gang shooting, and a meth lab.
Lt. Kelly Severide tries to keep his shoulder injury a secret as he helps a construction worker from a collapsed building. Meanwhile two teenagers are stuck in a vehicle.
The members of Firehouse 51 struggle to cope when one of their own dies in a fire. Lt. Matthew Casey and
Lt. Kelly Severide blame each other for their friend's death. Meanwhile Casey goes through a separation with Hallie and
Battalion Chief Wallace Boden has to make a crucial decision.